Vorshlag C5 & C6 Corvette Development + NewBalance and Rampage

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With the all important ball joints installed (below left), the arms could be reinstalled. These Moog replacements have an actual grease zerk for regular greasing, unlike the "sealed for life" OEM ball joints.



With the ball joints and bushings replaced it was finally time for the car's first Corner Balance, which we skipped after the MCS install due to track test scheduling and time.



Brad dialed in the corner balance on the morning of 5/17/22 using our digital scales and 175 pounds of ballast sitting in the driver's seat. He got the cross weights to 49.91% & 50.09%, which is pretty dang good (within 0.1% is as good as want to shoot for). The wacky thing is that the C6 weighs exactly the same as when we did our initial baseline stock weighing - 3117 lbs. It now has wider wheels and tires, bigger brakes, huge radiator, and some other upgrades. A little less fuel this time, though.

FITTING 295/30R19 HOOSIER R7 TIRES TO THE CAR

Right after the MCS coilovers were installed, a bit earlier in 2022, I asked Brad to test fit these 19x10" wheels t the C6. I assumed the wider 295mm tires would require some spacers to clear the shocks, and yes I know that this 295mm width size is "too big" for a narrow 10" wide wheel. But it was an extra set of very inexpensive 19" wheels I had for this car that we had set aside for this set of R7s long ago. In a perfect world these tires would be mounted on a 19x11" wheel, but that size wasn't available at the time for anywhere near what I paid for these 19x10s.



I also bought these Hoosiers for $300 for the set. Yes this set of Hoosiers should have been $1600 new in 2021, but I got them for a steal - after sitting for 3 years in storage I scooped up this "sticker new" set for a song after seeing them posted on FB marketplace. The long wheel studs that were installed on each corner would allow us to slip on some spacers as needed. It took a 1/4" spacer at each corner to make these work, nothing to worry about and the tires still easily cleared the fenders, as seen below.



I actually had these Hoosiers with me to use at both Track Test #6 on April 14th and Track Test #7 on April 28th, but unforeseen issues at both tests (rear brake pads disappeared at Test #6 and the control arm bushing popping out at Test #7) cut those test days short without any "Hoosier Laps".



Now that we had those issues fixed we could take then for Track test #8 - or so I thought...

BSP MOTORSPORTS ALIGNMENT - MAY 17-18, 2022



I called BSP Motorsports, a local motorsports install and alignment shop, and begged them to sneak my C6 into their alignment schedule. They got us in the same day that we finished the corner balance. The C6 was in and out in 24 hours and dialed in the maximum camber they could get with the stock eccentric adjusters up front, then balanced with an appropriate amount out back.


I was disappointed that even with this ride height on coilovers, all we could get was -2.3 deg camber on the left front (right front could get to -2.8, but again - had to balance to the low side), so that was what it was set to. The rear was set at -1.76 camber to balance the rear to the front. I asked them to set the front toe to "zero" and the rear to 0.28 deg toe in on each side (1/4" of total toe in). They got this dialed in, verified our corner balance, and I picked up the car with the trailer and loaded up that night to go to the track the next day...

TRACK TEST # 8, MAY 19, 2022

With the C6 loaded up I left at 5:30 am to head out to a Thursday member day at MSR Cresson. I was excited to finally get a session on the R-S4s with a proper alignment and the coilovers and bushings fixed, but also to run a session on the 295/30R18 Hoosier R7s. I had an outside hope of taking the C6 on these Hoosiers to a NASA TT event in early June at nearby Hallett, if the lap times looks halfway decent and the car felt sorted.



That was not what happened. I was the only car on track for the first session of the day, but I was fighting weird braking issues that were completely out of character for this car after we had sorted the ABS. What is going on on NOW?



After taking 3 thirty minute sessions and 24 laps on the R-S4 tires, I was not getting any faster. These 200TW tires just were not giving me much grip. After a string of high 1:24s I managed a 1:24.1, then a 1:23.4, then strung together a new personal best of 1:23.39 on the C6 with MCS RR2s, 275 RS4 tires, and new poly bushings.



I had a 60 minute delay during which open wheel cars and motorcycles ran 30 minute sessions, so I came in and started swapping onto the the 295mm R7 tires with the marked spacers. Didn't see anything weird (apparently I'm blind) as these went on then I was ready to go out at 10:30 am for a five lap stint. I needed to go out, scrub off the mold release, come in and check pressures, then do another quick stint to maximize lap time on the Hoosiers.



Right away I noticed an issue - after installing the R7 set the brakes didn't want to work, at ALL. Every time I stepped on the "whoa" pedal the ABS went into some weird hysterics and it wouldn't slow down. Was there a bad wheel speed sensor? Had the Mk60 gotten into its own sort of "ice mode" that I didn't think was possible?




It was getting warmer and my chance of running that "gold lap" on the R7s was dwindling. So I stayed out and limped the car to a new best lap of 1:22.933 lap, essentially not using ANY brakes. Then when braking into T9, the RF tire locked up briefly. Whoa... that was weird. I decided to come in, but I had just passed Pit In. So I limped the car around and at Ricochet I touched the brakes, and the right front tire locked up and stayed locked. I couldn't drag the tire around locked up like this, so I drove off the corner and parked it off the edge of the track in the dirt. The track workers had to send truck and trailer out and drag the car up onto the flat bed with a board under the RF tire. The brake would NOT unlock!



After unloading the car with the tire still locked, I quickly got to work trying to figure out WTF was going on. As soon as I jacked up the RF corner, the tire unlocked and spun freely. Removing the wheel it was then obvious that the front brake flex line was pinched between the front spring coils, and from the looks of the line it had happened many times before. This time it caught it just perfectly and once I applied brake pressure it locked that corner's caliper, hydraulically.



Once again the RoadKeeper camera had no audio on all video taken, so it is worthless. After I removed the brake line from the spring I drove around the paddock and it stopped fine, but that one Hoosier was trashed (now these cost $500 each) and I loaded up and headed to the shop for repairs. This was a complete sh!tshow of a track test.

BRAKE LINE REPLACEMENT, TIE ROD HEAT SHIELDS, CARBON LIP REMOVED

Later the same day as Track Test #8 I unloaded the C6 and we put it up in the air to diagnose what went wrong. Clearly I saw the pinched brake line but the ABS trouble light was on as well, so I asked Doug to connect the Mk60 to his Matco scanner.



With the ABS connected to the scanner he noted the usual logged errors - steering wheel sensor, VIN number issue, and CAN disconnected (which we have had ever since the Mk60 install) but there was also a logged error for a RF wheel speed sensor. That was likely from when the RF wheel locked due to the line being mechanically pinched. So the Mk60 noted it, which is good to know.



I had noted that the LF wheel hub that felt a little sloppy during my swap at the track to Hoosiers, and Brad also noted it. This was the non-SKF branded active hub we had on the front, so I ordered another SKF.



That took a week to arrive but we got that swapped out a couple of weeks later. Now the car would have 33 spline SKF X-Tracker hubs on both fronts and 30 spline non-SKF rears. I am still planning to upgrade the rears but I will have to buy 33 spline axles and swap those at the same time. Again - learn from my mistakes and if you are upgrading to a Mk60 and need the Active hubs, just buy all four up front (and swap the axles if you have to) and save yourself these troubles. Being cheap always costs money!



The brake line was once again pinched in between the spring and the upper perch, as I drove the car in. I guess this is a possible downside to converting to coilovers from transverse springs - there is no factory bracket to keep the stock line from touching the shock because they don't have a spring there. It keeps wanting to flop over that way on the RF corner, and it likely had a slight twist in the flex line that made it want to lean that way. So while we could have just twisted the line to not fall into the spring, I wanted to fix this right.



We also burned another tie rod. This is happening because we are seeing alarmingly high front brake rotor temps, approaching 750 def F, and the tie rod boot is very close to the rotor on these cars. So we ordered another new tie rod and I asked Brad to make a stainless steel heat shield. We keep 316SS sheet on hand for these things and it was a relatively easy design to cut, bend, and install between the tie rod nut and the spindle. Now we have an air gapped shield using metal that does not like to transmit heat.



A pair of Stoptech stainless brake flex lines were ordered and Doug made this little "deflective cover" out of aluminum sheet (softer than the line's jacket) that is clamped to the upper control arm. This will keep the line from getting into the spring again, but shouldn't damage the stainless flex line. We are keeping an eye on this every time the wheels are off, of course.



The brake rotor temps I logged at the last two track tests were really high up front, and it was obvious why - the Extreme Dimensions carbon fiber front lip was blocking the factory front brake inlet ducts. This lip was also quasi-illegal for SCCA T2 class, so instead of trying to modify this unit I asked the guys to remove it.



This is now how the front brake cooling flow should work, instead of the tortured and half-block pathway that the splitter lip caused. This also allowed us to reinstall the OEM air deflectors on the sides. I will continue to take IR gun temps from the rotors and should see a significant drop in temps by removing this - but could also see lower front downforce. We will see.



It was also time to install the Jongbloed 18x11" front and 18x12" rear wheels. These went on with a used set of Yokohama A052 tires in 200TW, but in a wider 315/30R18 size. I purchased these tires in 2020 to use on Koenig's C5 for the Optima autocross event but the durometer readings were still good and they only had about 5 autocrosses on them by this point.



And while I had planned to modify these nozzles on the factory brake cooling at a later point, the wider and taller 315/30R18 tire was rubbing the plastic here when the wheels were turned, so I asked Doug to lop these off. This gained clearance for the tire when turning AND possibly opened up the airflow from the brake cooling.



We ordered these max-fitment wheels a year ago, long before the coilovers were installed. The measurements were fudged with the expectation we'd run a small spacer to perfect the fitment.



At the end of the day on May 25th I loaded up the C6 with the Jongbloed wheels on for the first time. Sure, I should have left the "control tires" (19x10/275mm R-S4) on the car to get a proper updated lap in, but damn it I was tired of the slow ass Hankooks. They take too many laps to get up to temp and they just don't ever make more than 1.15g lateral. I'm ready for more grip, but the Hoosier set had that one flat spotted tire. So the 315mm Yokohamas are the new control tire. Let's see what they can do!

TRACK TEST #9, MSR-C, MAY 26, 2022

Only one week after Track Test #8, and ALL of the repairs and updates shown above, we were back at Motorsport Ranch Cresson for test #9. After the previous two track tests were scrubbed early due to parts failures, I really was looking forward to a less troublesome day. I also had two customers meeting me at the track, one to test drive his Cadillac daily driver and the other one was the new owner of my 2018 Mustang GT, who came back to have us T56 Magnum swap the car (along with many other upgrades). I was there to make sure the car was working well on track after a bunch of changes we made. I include a "guided track day" for every major build we do, and even though this one was a bit less than "major" I still wanted to be there to diagnose any issues and/or do some coaching at a track he had never driven at.



I arrived before 7 am and had the 7:30 am session all to myself. I fueled up the tank for several sessions and went out before the track really had a chance to warm up. I broke up each 30 minute session into two stints - because the tires were overheating after 3-4 hot laps. I was also adjusting tire pressures and checking the brakes, since I had such problems the last two track tests with those. I came in quickly after my first stint (1A) and jacked up the front to look for any tire rub, nothing worth noting.

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Project Update for July 26, 2022: This update is only 6 weeks since the last one, but is still jam packed with work on our narrow body C6. The past few months have been a very productive with upgrades and work on this project - and it is where a bulk of track lap time improvement has been unlocked. The C6 is now a LEGIT fast track car, even competitive in a certain Time Trial class. I'm as shocked as anyone, with as hopeless as the first 10 months of this car went!



In this update we will cover work to this C6 on the following systems: upgraded control arm bushings, ball joints, a "real" alignment done by a Motorsports shop, 2 more track tests, an exhaust + header + cold air upgrade, custom dyno tuning, a second seat install, 6-point harnesses, a fire bottle, transponder install, and an SCCA Time Trial event. We also finally got the Jongbloed wheels and 315mm Yokohama A052s on the C6 - as well as some 295mm Hoosier R7s, but that Hoosier test was a hot mess, which I will explain.



We pick up here after Track Test #7, which was on April 28th, 2022 - where a 16 year old stock rubber front control arm bushings popped out. But first, I had a bit of an epiphany with respect to "what should we do with this C6?", specifically, what class should we build it around? I found a surprisingly good class to run it in a rather surprising series. And even more shocking - I won the first TT event we entered, by a healthy margin. Let's get started!

PICKING A TIME TRIAL SERIES & CLASS FOR THIS C6 : SCCA TT TUNER 2

After being out of the Time Trial game for nearly 3 years I was really missing some form of Motorsports competition. Sure, I'd done a few autocrosses in 2020, 2021, and even a couple in early 2022. Below are two events I won this year. In the C5 I won my class and set FTD at left, and won the class and set 3rd fastest time of the day in thew '22 BRZ at right. So while I don't totally suck at autocross, the limited amount of seat time in these parking lot events wasn't "scratching that itch", even with some solid wins. What I really needed was some road course competition, and the most affordable road course events I have found over the last 30 years are Time Trials.



If you have followed my social media and forum posts for a while you would know that over the past 15 years I have trended away from autocross (which I started in 1987) and towards Time Trial events (I did my first TT events with NASA in 2006 and other groups as far back as 1991). While I will always be an autocrosser at heart, and will continue to compete there, for business reasons and my personal driving skill set (or lack thereof) I think my time is better spent doing Time Trial.



My "go to" TT series NASA has over the last 15 years become much more focused around Hoosier DOT tires as the the basis for all TT classes, from TT1 to TT6, and showing up on 200 TW street tires will get you relegated to "class filler". I did two seasons of events with NASA Texas (2018 and 2019) in my '18 Mustang GT (above left) on 200 Treadwear street tires on Day 1 and would switch to Hoosier A7 and R7 tires on Day 2 of a NASA weekend. The difference in times was always around a second per lap, but I noted that without aero and gutting the car to get on the edge of the Power-to-Weight ratio, I was largely uncompetitive in NASA. On the other hand, from 2012-15 we ran our 2011 Mustang GT (above right) in NASA TT on the max width Hoosier A7s, with full tilt aero, and at the edge of the power-to-weight ratio - and dominated TT3 class, setting 16 class track records. NASA TT is really geared towards the super serious, not dual purpose street/track cars like this C6.



And while NASA has tried to offer parity with some "tire equivalency" power-to-weight modifiers for TT in 2022, it is virtually impossible to do this right. The breadth of grip levels within "200TW" tires is huge, and the difference between 200TW and R7s is also pretty large. We have seen 1.15g on the R-S4 and 1.30g on A052s, both marked and classed as 200TW tires. Hoosier R7s and A7s tend to make closer to 1.4g grip, which is another step up. NASA has seen unintended secondary effects from their "tire modifiers" in TT that added even more class instability and cost.

I'm not willing to play that game at the moment, especially with a legit street legal car like this C6 - which I have promised my wife and crew at Vorshlag that we will NOT do the following to: cut up, add aero to, gut the interior of, add a cage, or swap the engine. This was supposed to be an easy "tweener" track car build, to allow Amy and me to have some fun track time while our REAL cars are being built: her '13 FRS and my '15 Mustang. It has already gone past the "easy" but it is still streetable with a full interior, functional emissions, cold air conditioning, roll up windows, and yet monster improvements in suspension, brakes, and more.

The sad truth was that the lap times in this little C6 were pretty uninspiring on the 275mm R-S4 200TW tires, and the bone stock 360 whp engine was a little underwhelming as well. So after we tackled the troublesome ABS issue and got the MCS coilovers on, I started looking at places to race this in Time Trial. Looking at the power and weight of the car (3320 pounds with driver + 360 whp) it was pretty much doomed in NASA TT classing - just like my 2018 Mustang, it was it was stuck DEAD in between their TT2 and TT3 classes...



Each NASA TT class has a strict power-to-weight ratio you have to build towards - TT3 is 10:1 while TT2 is 8:1. Like the 2018 GT, this C6 was stuck almost exactly at 9:1, right in between two classes. I spent 2 years trying to get around that limitation in the red Mustang, jumping between TT2 and TT3, and was largely unsuccessful and frustrated. I found once again that to be competitive in NASA TT you have to CUT ON THE CAR to fit max width tires, GUT the interior to get the weight closer to the P-to-W limit, add REAL AERO that wrecks the streetability, and of course RUN HOOSIERS in widths that will cost $500-600 per corner.



Of course you can always "aim lower" and build towards a slower class. We could have run this C6 on 275mm wide Hoosiers and either ballasted up with weight and/or detuned the 360 whp engine to make the 12:1 p-to-w ratio required to run in TT4. But I've already done too many seasons in "slow TT cars", with my E46 330Ci (in TTD and TT4) and C4 Corvette (in TTC), above. I just don't enjoy driving slow cars, even if they are "more competitive in class."

So I wasn't down with making this C6 even SLOWER to fit within TT4, then running $2000/set R7s that would wear out more quickly because they were needlessly narrow. I know we can fit 315mm tires under the stock narrow body fenders, and by damn THAT IS WHAT WE WILL RUN. And I know there is some easy power we can unlock with headers and a few bolt-on tweaks, and I want to DO THAT TOO!



I had written an article in 2018 about SCCA Time Trial rules and suggestions (linked here), but I have updated my thoughts on that series in 2022 in this post. While I was a critic in 2018 when SCCA National first rolled out their new TT series rules, they have made some significant improvements over the last 4 years - and more pressing, my home SCCA club Region adopted the National TT rules for 2022. So while I had fun and success in my 2018 Mustang GT and the FRS running the regional SCCA TT (see above) for a few years with their unique Regional rules, if I wanted access to proper 200TW based TT events locally (Texas Region does 7-9 events per year - at tracks all local to me!) I would have to adapt to the National SCCA TT rules.



So we dove into SCCA's TT rules in 2022. SCCA TT has 4 categories: Sport, Tuner, Max and Unlimited, with classes within each. The base Sport category is far too stock for my tastes or our business, Tuner was like Street Touring autocross classing (which I ran competitively in from 2004 through 2013 in many cars, including the two above), Max was pretty wide open but still 200TW based, and Unlimited was anything on Hoosiers or other mods beyond Max. Due to some wild price increases with Hoosier during the Pandemic I am going to largely stick with running 200TW tires for a bit. And while Max looks like fun (full suspension, aero, gutting, flares, cages, and virtually unlimited power upgrades), I am trying to keep this C6 a street legal car and again, not cutting / gutting / swapping engines. Maybe one or our other cars being built will run in Max.



After weighing the 4 possible categories we picked SCCA's Tuner category for the Corvette, and the class where this narrow body C6 fits is called T2. T1 is for widebody C6 Z06 cars, and pretty much all non-supercharged narrow body C4/C5/C6/C7 cars go into T2. The T3-T6 classes are all for less powerful cars. Each class in Tuning has a Max tire width, and in T2 it is 315mm, and of course 200 TW tires. I have been doing a LOT of testing and driving on 200TW tires for the last 2 decades, so that fits. Mods allowed include common bolt-ons like headers, exhaust, cold air intake kits, seats, wheels/tires, big brake kits, and pretty unlimited suspension changes.



Luckily almost everything we had done to the C6 was all legal for Tuning 2 class, and the rules committee was open to making some allowances if you had good arguments. Like the transverse leaf to coilover swap - it wasn't legal in Tuner until after I sent a letter and made a case for precedent from SCCA Street Touring autocross class, which had allowed this swap several years earlier. And then the TT committee made a change within about a week - that was refreshing! One limitation in Tuner is around bushings - metallic busing replacements are NOT legal, like the Street Touring Solo classes, which influenced the decision below... (probably for the better)

CONTROL ARM BUSHING FAILURE & POLY UPGRADE

After track test #7 it was clear what failed, but unclear on which way we would go from here. We got to work on the fix right after that test.



There was one upper control arm bushing that had pushed out of the sleeve under heavy braking on the not grippy R-S4s, and this would only get worse the more we ran with grippier tires on this car. Replacing one bushing with another OEM unit would be beyond foolish, as this is a very common failure. We have had customers who tracked their C6 cars that had multiple OEM bushing failures when new, and replaced them repeatedly under warranty. The "common" fix is to swap to spherical bushings on all of the rubber bushings.



I spent entirely too much time looking at these options, as "everyone on the internet" goes with sphericals to replace the rubber bushings. Two grand for the spherical bushing kit and it is a LOT of work to install these, often including a step to send the control arms to the manufacturer to have them honed to precise size. The sphericals were not legal for SCCA TT Tuning class, so that option was out - but I didn't want to use these for other reasons. The Delrin bushing kit from Ridetech would be legal but at $1400 it is still as much work and likely will make the ride quality as bad as the metal sphericals.

The downside to both of the above options is increased NVH (noise / vibration / harshness) and a RAPID wear and replacement cycle. We had a customer stop by in his C7 last month who had been chasing a very loud rattle in his C7, which had spherical bushings that replaced the OEM rubber units. It took about 30 yards of driving for me to isolate what had happened. I got out, popped the left front tire's sidewall with my fist - BANG! BANG! BANG - and showed him how to replicate the noise. Yea, the sphericals were worn out after one year of use. The noise was LOUD. You see, unlike the sphericals we use in top mounts, Corvette control arm bushings are MUCH closer to the ground. As such, the unsealed metal spherical control arm bushings get sprayed with water/rain and mixed in with that is grit and sand. That EATS metallic bushings FAST. Luckily, Tuning doesn't allow this, so polyurethane or Delrin were our two options.



To keep this C6 from turning into a "miserable to street drive" car, plus the Tuning class rules, and due to the fact that the C5 above (that I have driven many times) got polyurethane bushings that we installed SEVEN years ago without issue, I went with the same Energy Suspension bushing kit we used on that car (the C5/C6 bushings are identical). The Energy Suspension bushings for the C5/C6 come in two colors (red or black, no functional difference) and there is a kit for the front (ENS-3-3176) and another kit for the rear (ENS-3-3177). All in you are looking at about $150 for all of the parts.



Normally I go for the RED to show the bushings better in pictures but that color was out of stock, so we went with black (add an R to the end of the part number kits above for Red, add a G for Black). They come with some small packets of grease but I'm going to show you a trick to make these poly bushings SQUEAK FREE for life - it involves adding grease zerks to each bushing.



This section of "installation tricks and tips" for the poly bushings got so huge that I pulled it out into it's own post, which you can read here. I recommend that if you plan to own a C5/C6/C7 Corvette. Long story short: any bushing upgrade is a pain in the ass but Poly has the least downsides and lowest cost (by a factor of 10), and this upgrade has been flawless for months of track tests and Time Trial events since.

NEW BALL JOINTS & CORNER BALANCE

During the control arm bushing upgrade above, I noted that several ball joint boots were cracked and falling apart. None of the ball joints were "bad" yet, which is why it was never noted in our pre-track inspections (where we wiggle and shake ball joints and wheel bearings), but it was time to replace several of these. Tracking the right part numbers down took a little time, and we had to order one of these twice - which set back my track testing schedule. See, I was eyeing an SCCA Time Trial at ECR on June 18th and this was pushing out my timeline.



With Jason's help we tracked down the right ball joints and Doug was able to replace all of the worn ones. Couldn't find just replacement boots, which is all most of these needed, but we replaced just the bad ones and moved on.



I picked Moog replacements, which is a brand we have used many times and trust. There were two front upper ball joints, one rear lower ball joint, and one tie rod that had a burnt boot.



These are usually changed with the control arms out of the car. The old ball joints on the C6 did NOT have snap rings retaining them in place, but some cars do. These just pressed out and the new ones pressed in. Doug used this massive C-clamp style ball joint press on some, and others were pressed in/out using out 30 ton air over hydraulic press.

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REAR BRAKE PAD + SMALL HYDRAULIC LEAK FIXES

The next week we brought the C6 in to swap out the burned up junk pads and put the R10 G-LOC pads back in, which seem to be wearing much better.



A small brake fluid leak was noticed at the Mk60 ABS unit, specifically at the ATEC sourced pressure adapters. Why this would have an O-ring is a mystery (it wasn't supposed to), so we removed both of those and replaced them with copper crush washers - and it has been 100% leak free ever since.



Considering how many lines / fittings / flares were changed this swap, it was remarkable how well this hydraulics work was. Thanks Brad!

TRACK TEST #7 - APRIL 28, 2022



At this point I am going to the track in this C6 pretty regularly now, and only two weeks after test #6 I went back to re-try my hand at that "best R-S4" lap time on the MCS coilovers. Once again I brought the Hoosier R7 set to swap on after I nailed that elusive 1:22 lap.



This time the car had rear brake pads on it, but the day did not go off without a serious hitch. I was on my third stint in the second 30 minute session and turning into Little Bend (a quick right hander) I heard a "pop" from the left front corner, then the car lurched to the left by one car length - putting my line in the dirt. Nothing hurt but my ego, and I came in knowing that a control arm bushing likely popped out. And that's exactly what happened.


I wasn't surprised as we have seen this happen on C5 and C6 cars regularly over the years, and we had planned to swap bushings after this track test anyway. This bushing issue cut my testing short with a best of 1:23.828 lap, only 2 tenths faster than the best at Track Test #6. I was just getting warmth into the tires and track surface but that 1:22 lap eluded me again! And once again I had video that was junk - no audio this time. I'm really getting sick of the RaceKeeper camera now.



Jerry was driving his car on the Michelin street tires and asked me to take a few laps with him riding shotgun, to see if I could find some time. Who says "no" to some laps in a C7 Z06 with the supercharged LT4 V8? This was just three fun laps, talking and joking with Jerry, where I pushed the tires and brakes maybe 80-90% and short shifted the engine by 500 rpm.



The on board "PDM" video logger showed a best of a 1:19.88 vs my AiM SOLO showing a 1:19.933. All in-car video taken in the C6 had no audio, so it is worthless. The above right video shows a quick sneak peak at what went wrong, as I was in the paddock looking for answers. Nothing I could fix that day, so it was time to head out.

LAP TIME PROGRESS - MSR 1.7 CCW

Over the last year we have taken this bone stock base model narrow body LS2 C6 - the worst variation they made in this generation - from a 1:28.7 lap down to a 1:23.8. That's a FIVE SECOND DROP with a pretty tame tire (275mm Hankook), coilovers, and an ABS fix. There is a lot left on the table (we've already gone 2 sec quicker - I will show that next time) but we're making real headway and got this coupe faster than the Spec Miata lap record... whew!

This list of best shows the progress on our little C6 from Test #1 to Test #7, with nearly each one on the same set of 200TW Hankooks. The 3 other Corvettes I've driven are shown in the ranking, as well as the 2022 BRZ I drove on Test #5, and all laps for this C6 are in bold:

• 2006 Corvette, Baseline Stock Lap Time, 245/275 500TW, stock pads tires (Test #1), 4/9/21: 1:28.743
• 2006 Corvette, G-LOC R12/R10 pads, 275 Hankook RS-4 tires (Test #2), 4/18/21: 1:26.248
• 2006 Corvette, G-LOC R12/R10 pads, 275 RS-4 + "Bad" Alignment (Test #3), 5/27/21: 1:26.823 (slower!)
• 2006 Corvette, G-LOC R12/Brake Best rear, 275 RS-4 / 275 500TW (Test #4), 8/20/21, 1:30.015 (even slower!)
• 2022 Subaru BRZ, MCS TT1 coilovers, 245mm RT660 tires, otherwise stock, 4/24/22: 1:26.927
• 2006 Corvette, G-LOC R12/R10, 275 RS-4, Mk60 ABS, stock suspension (Test #5), 4/24/22: 1:26.4
• 2006 Corvette, G-LOC R12/R10 pads, 275 Hankook RS-4 tires, MCS RR2 coilovers (Test #6), 4/14/22: 1:24.072
• 2006 Corvette, G-LOC R12/R10 pads, 275 Hankook RS-4 tires, MCS RR2 coilovers (Test #7), 4/28/22: 1:23.828
• 2012 Corvette C6 Z06, Carbotech XP10/XP8 pads, 285/335 MPSS, perf alignment, 9/16/16: 1:22.63
• 2017 Corvette Grand Sport, Z07 aero package, 285/335 MPSS, perf alignment, 9/16/16: 1:21.89
• 2017 Corvette Z06, Supercharged LT4, CCM brakes, cooling upgrades, 285/335mm MSC2 tires, 4/28/22: 1:19.933

WHAT'S NEXT?

I better stop there - this is already a MASSIVE update that took me nearly 3 days to write, compile and edit. We've already done two more track tests, upgraded to poly bushings, fitted the Jongbloed wheels and large 315mm Yokohamas, and dropped another 2 seconds. We have also had the car laser aligned at a motorsports shop, removed the carbon splitter lip, and tweaked the brake cooling. In the last two weeks we have added long tube headers / catted X-pipe, dual 3" Z06 mufflers, and a cold air intake, changed the thermostat - then had all of that tuned. More power and better noises are always fun!



We're also looking ahead to additional mods that are next, like a better fixed caliper brake upgrade - with lots of parts here to test fit and modify. We are keeping the "dual purpose" street/track theme as the main goal, so street legal and safe to drive around town. And we found a potentially decent class to compete with this car in SCCA Time Trial - their Tuning 2 class. I am going run this at ECR with the Texas Region SCCA TT this coming weekend in that class, so we'll know soon if we have made a winner or a loser!

Until next time,

Terry Fair @ Vorshlag

[Fair!]

continued from above

Brad was able to sneak this BMW M3 yaw sensor behind the ash tray, with some careful trimming. This is centrally located in the chassis, where it needs to be. The Mk60 system can be mounted pretty much anywhere, but it gets crowded under the hood. We spent some time looking all over the chassis for a spot to mount this, and noticed that some C5 / C6 Mk60 swaps were put back behind the LF wheel, where the windshield washer bottle normally goes.



So that's where Brad mounted the ABS brick, on another custom bracket he built with high temp isolator mounting bushings. On a pure track car / race car these are often moved inside the chassis, as a heavy crash could damage the ABS unit or lines. But on a street car this is a common spot.



The ABS brick is marked in German but it is easy to find the translation. Brad made new brake hard lines from the master cylinder (below left) to the brick, and from the brick to the 4 original brake hard lines under the hood.



After all 6 brake lines are connect it is time to splice in the 4 pairs of wheel speed sensor wires. Then add the two 30 amp fuses to power the harness, mount the OBD port, and then install the ABS trouble light (if it is "on" something isn't right).



That is a quick overview of the Mk60 swap on a C6 - we will put all of this and more into an separate ABS swap forum thread later.



We did our initial testing with the crappy stock wheels and 500TW tires, but quickly moved up to the Hankooks. We left the front fender off during the shake down testing on the street, and we did have one tiny leak that needed a new tube nut to fix. Now all you need to make this Mk60 work is the correct style of wheel speed sensors, which I will cover below, as well as a tiny bit of programming.

C5/C6 WHEEL HUBS + ABS CHANGES

The C5 Corvette had an integral wheel hub with a speed sensor built within, and that generation had a certain type of speed sensor type called "passive" (grey or black sensor wire), which carries over into some C6 models (like our base model 2006). The 2009+ Corvette Z51/Z06 model cars changed to an "active" type of sensor (yellow wire), but the wheel hub itself was physically identical. Well, there were OEM front and rear models - with the rear units having splined opening of either 30 or 33 splines.



In the above left pic you can see some OEM "front" hubs (grey wire) from our C6 without the splined center hole, and the "rear" style with the splined opening (yellow wire) - which can be safely used on the front without a halfshaft/stub axle holding them in place. And of course we always like to put ARP long wheel studs into these for various reasons - when ARP has them in stock.



In the same month we were doing the MK60 ABS swap / hub upgrades on the C6 we were also doing the same work on a Gen I CTSV, and it needed to move to these "active" hubs for the Mk60 to be able to read the wheel speed signal correctly. This CTSV needed 30 spline rears, as did our base C6... which was tricky to get the Active hubs for - and you cannot get SKF X-tracker hubs in Active sensors in 30 spline, it simply does not exist. So on the back of that CTSV and the back of our base C6, we had to use "off branded" active 30 spline hubs.



And that is the lesson we have learned - you ALWAYS want to use SKF X-tracker hubs on a C5 or C6. And yes, they cost 2-5x as much as the cheap China replacement hubs, but that's because they last 10x longer or more. The price shown above right changes WILDLY every month and the $210 cost for 33 spline X-tracker hubs has been as high as $300 recently. Just prepare to spend that amount or have constant failures.



I was "being cheap" and ignored the "only use SKF" advice on our C6, but we had 4 out of box failures with other brands. The bearings were either notchy/loose right out of the box or the speed sensor circuit was dead. We started checking resistance on each hub before we did the work of swapping the ARP studs and installing the hubs, to save time sorting through junk.



I bought one SKF 33 spline hub for the front and one "C-TEK" brand, and the C-tek lasted ONE DAY on track, then it had movement in the bearing. So now we have two SKF 33 spline X-tracker fronts on the C6, and two off branded rears. To swap to 33 spline SKFs out back we need to swap the rear axle shafts, and that is on the short list for the future.



Once you have all 4 wheel hubs changed to the yellow wire "active" sensors you need to connect to the OBD port that came with the Mk60 wiring harness, tell the ABS brick "you are a 2003-06 BMW E46 M3", then clear any fault codes. You can also rotate each wheel and see wheel speeds generated in real time, with the right scanner. Then it is time to go do some brake tests! That was a good day, once we had the C6 stopping reliably at 1.15g with zero lockups. Huge win!

TRACK TEST #5 - MARCH 24, 2022

Amy and I drove the narrow C6 for the first time on the Mk60 ABS and 1 year old 275mm RS4 tires. I also drove a customers 2022 BRZ with MCS TT1s and 245 RT-660 tires.



In the brief video below I explain the "feel" of the car, the performance of the brakes, and do a quick walk around. It was a very cold morning (34F) and it took a lot of laps to get the R-S4 tires up to temp.



That cold ultimately hurt my lap times until a later session when it warmed slightly (the AiM worked but the video camera took a crap). I managed a best of 1:26.4 in the C6 with the ABS working, but still the stock suspension - not what I had hoped, and while some 1:25.X predictive times flashed by I could never string the lap together. All of the video from the C6 was hosed, but I got the '22 BRZ down to a 1:26.9 on my single solo lap on some very hot tires.



Driving two very different cars back-to-back showed me several things about the C6 - and as you can see the BRAKE DIVE is a bit extreme now, since the brakes actually work. The car is wallowing around like a pig, and it needs REAL spring rates and REAL dampers (so we installed the MCS coilovers next).



The braking performance on the BRZ (see video above) with stock calipers and track pads was also better than what the C6 can do at this point - we needed a more aggressive pad on the C6. The BRZ on MCS coilovers was so much flatter in corners, under braking, and easier to drive too. The gen 2 BRZ at 2750 pounds, MCS coilovers, Falken RT660 tires, and making 200 whp, and it is damn near even on track with the 360 whp C6 Corvette! (on worse tires and stock suspension) The C6 is also still slightly slower than the Spec Miata lap record (1:25.9) at this point - we need to fix this, straight away!

MCS RR2 COILOVER INSTALL

Just a few days after track test #5 (March 29th) Brad started on the MCS coilover install on our little C6. These shocks have been sitting here patiently for nearly a YEAR while we sorted all of the ABS problems, but at long last it was time for the BIG upgrade that I felt would unlock a lot of lap time in this car, all by itself.



This mod is one we have done on countless cars and it typically unlocks 2-3 seconds per lap at MSR on the 1.7 CCW course. We utilized 700 #/in front springs and 650 #/in rate on the rear, with Vorshlag spherical top mounts at both ends. This is our softest coilover spring rate we offer, but with the spring rate of the OEM springs in the 150-200 #/in range, this is still massive change. Removing the transverse leafs removes a lot of "swaybar effect" (more on that later).



I was hoping for a small weight drop getting rid of the huge composite springs, but with the remote reservoirs the weight change was nearly a wash, with a 0.1 lbs change up front and 1.0 pound weight drop out back - nothing worth bragging about. We chose the remote reservoir double adjustables as I personally feel these give the most advantages of coilovers for the cost - the remotes increase shock travel, radiate heat away from the fluid, include separate Rebound and compression knobs, but without the cost of 3- or 4-way MCS dampers.



After checking / marking our "initial" specs (camber, toe, & ride heights at each wheel) the C6 went up on the lift and the stock transverse springs and shocks came off both ends. The front spring was a CHALLENGE to get off - Brad had to disconnect the lower arms to let them hang to be able to fish the spring out. The rear spring came off by compressing the control arm on each side, disconnecting, then letting the suspension droop.



We make spherical top mounts for both ends, but we have a unique way to gain "bump travel" and spring room on the front. We have MCS make the front shock inverted, with the body at the top and the spring on the bottom portion - we need that room to clear the upper control arm. Well we need a little more room, so we have a tool we include (top left) to mark the offset center hole to be drilled. The CNC cut plate is used to mark two new upper mounting holes, then those are drilled and the plate is bolted in place. Then the new center pilot hole is drilled offset to the inboard...



Then a hole saw is used with this 1/8" pilot hole to make a slightly larger diameter hole offset from the stock shock mount hole. This allows the bulk of our upper spherical mount to sit above the top of the "shock tower", gaining suspension travel and removing a rubber shock mount bushing from the damper load path. The offset nature of the hole kicks the top of the front shock inboard to help clear the upper control arm, too. It works really well on all C5 and steel framed C6 chassis cars, but not the aluminum framed C6 Z06/GS/ZR1 cars.



Out back we have MCS make the rear shock "non-inverted", with the shaft (and rebound knob at the top. We make our upper spherical shock mount to bolt into a "blind pocket" on the rear of a C5/C6, then ask our customer to drill a pilot hole then a hole sawed opening to be able to get to the rebound knob. We CAN order the rear shock inverted, with the Rebound knob at the bottom and no need to cut the access hole - but getting to that knob is so much hard, as you have to jack up the car to get to it.



In the rear I wanted to mount the remote reservoirs (with the compression adjuster) inside the trunk area to - also for ease of access to that knob. To do that Brad drilled a hole through the floor (which we mapped out carefully would not intersect with anything) to pass the reservoir and hose through. The "quick release" connector on the hose is deceptive - to disconnect that you have to discharge the 180-300 psi Nitrogen charge, then disconnect, then pass the hose through a smaller hole, then reconnect and re-charge. With this 1-piece aluminum spiral cover and small grommet we can just unbolt the cover and pull the whole reservoir through, when needed.



The finished install of the rear knob access hole and reservoir pass through hole + cover is shown above left. We left the rear carpet out for now, and just tied the reservoir to an interior composite protrusion for now. I can (and have) adjust the rear Rebound and Compression very quickly, just by popping the rear glass hatch. Up front (above right) the reservoirs were temp mounted to the stock airbox, as the hoses are long enough to snake under the frame rail and reach that "cooler" spot under the hood.



Brad finished up the install, ride height setup, and corner balance on April 1st. If you notice the front ride height is TALLER than it was before, as some previous owner had SLAMMED the front ride height on the stock spring adjusters. I drove the car to lunch a couple of times and really liked how it felt, how it cornered and slalomed, and the ground clearance was improved. We got busy but on April 13th I got the car back in the shop and Brad did a string alignment, to get the alignment in the ball park. Then we loaded the car into the trailer to do some more track testing the next day...

TRACK TEST #6 - APRIL 14, 2022

I drove the C6 on the 275mm RS4 Hankooks to test the MCS RR2 coilovers and newly installed Mk60 ABS. The string alignment Brad did found then fixed the wacky rear toe out issue (finally) that plagued this car since track tests 3 through 5. That rear toe out of a half inch in the rear had been making the rear super unsettled and loose. Coupled with the shoddy ABS programming it made this car a bear to drive, but all of that was better now with the alignment better and the new MCS coilovers in place. This was the day on track I began to hate this car a LOT less!



My plan was to start the morning off with a session on our "control tires", the 275mm Hankook R-S4s, then install some brand new 295mm Hoosier R7s on the other 19x10" wheels to throw down an even quicker time. And I chased a good lap time for 2 full sessions on the Hankooks, making driving mistakes and fighting rear brake issues.



I wanted to see the best the Hankooks could get to on the MCS RR2 coilovers and Mk60 ABS. I made a whopping 37 laps on these tires and put a tank of fuel through this car trying to catch the car's best lap time - saw 1:22.X predictive lap times more than once, but all I could complete was a best lap of 1:24.0 on the RS4 tires. I had a couple of weird braking issues that kept cropping up - now what had changed? I even had a couple of pretty big "offs" when the brakes seemed to weirdly just lose stopping power after 4-5 laps of driving.



I came in to both "take a look" at the brakes as well as swap over to Hoosiers, and that is when I noticed the issue - the "parts store" brake pads had been left on the rear and I burned those down to the backing plate, which was why I was fighting brake issues all day.



The weather was pretty cool and so was the track temp. This in-car video of my best 1:24.0 lap is in this video, linked above. At this point in the car I know something is going on with the brakes, but I hadn't pulled a wheel off to see the completely shot rear pads. I took a cool down lap after the 1:24 lap and then put in a hot lap, when I saw the 1:22.6 predicted lap pop up. I braked into the last turn (Big Bend) where I always do, but the rear pads were metal-to-metal by then and I went right off the corner. That's when I went in to change tires and noticed the pads, then I just loaded up and went back to the shop.

continued below

[Fair!]

continued from above

We ordered the wheels in 18x11" for the front and 18x12" for the rear, with red centers. If we got the numbers wrong we could re-order the rim halves and get them adjusted narrower or with differing offsets, but that's still a costly change to make. So in late July 2021 we mocked them up on the car without tires...



This is the best way to check a new set of wheels - before tires are mounted. Some wheel makers even put big decals on the wheels that say this "if you mount tires to these wheels you own them!" So we mocked these up on one side of the C6, with one front and one rear.



They fit pretty well straight away, but I was worried about some inboard clearance with tires mounted. Sadly the 315/30R18 Yokohama A052 "200 TW" tires I wanted were on backorder (and stayed that way for months) so we would have to wait to mount those up. Plus I wanted to complete all of our initial track test and ABS testing on the harder R-S4 tires. I figured this would be handled in a couple of months but that stretched out into early 2022... as did the backorder on the A052s!

BASELINE DYNO RUN - BONE STOCK LS2!

I dropped off the C6 for a baseline Dynojet rear wheel dyno pull on June 15, 2021 at True Street Motorsports. They don't really do much LS tuning anymore but they got me in for a few pulls, which I like to do on all race cars initially before any mods or annually - as sort of a checkup, or annual physical. Anything weird seen in the dyno, or unexplained changes year to year, are always worth exploring.



As I said in my first post in this thread our 2005 C6 Corvette 6 speed made 355 whp (I've long lost those charts) back in 2004, so I had hoped this 45K mile 2006 would make a similar number. And it did - it made 360 whp / 367.5 wtq with the harder SAE correction factor.


With the more generous "STD" correction factor it made 366.5 whp and 374 wtq - but nobody uses STD except drag racers. NASA and most road race groups use SAE, which is almost always lower. This baseline will be compared to later, after we installed long tube headers + Z06 exhaust + cold air intake and filter.

CARBON FIBER "ZR1" STYLE FRONT LIP (FAIL)

In July 2021, around the same time as the seat install was wrapping up, we received then installed this carbon fiber front lip from Extreme Dimensions / Carbon Creations. I ordered these + some ZR1 style side skirts and tire walls, and it was ... well, a mixed bag. I noted it as a FAIL in the header above for one reason (brake cooling blockage) but it had some good features, too. Let me explain.



Visually the part looked great, and it was marketed to fit the "narrow body C6" front nose. And it did indeed fit the narrow body nose - but sadly the inlet scoops were NOT lined up with the brake inlet ducts under the nose (see bottom right). So the scoop section has to make a detour outboard to shovel air to the brake cooling inlet (see above right).

And the bottom line is - THIS DOES NOT WORK well because this splitter lip effectively BLOCKS the brake cooling almost completely. I didn't want to believe this as I spent a decent chunk getting these parts, and we spent a lot of time installing the splitter, but track testing of rotor temps with the splitter on-off-on (A-B-A) proved this. Just took us several months to get to the point where the brakes even WORKED to be able to test that.



Above you can see the lower OEM deflector plastic sections on the ends we had to remove to be able to fit the splitter in place. It has zero instructions so you have to just fumble your way into finding this. Sadly these flaps help create a high pressure area in front of the brake cooling inlets (above right), and removing these outer lower air deflectors makes the brake cooling a lot less effective - but so does nearly blocking them altogether. On the plus side, removing these side flaps does make it MUCH easier to strap the car into the trailer without scraping the hell out of your arms. That might not seem like a big deal to you, but when you load or unload a car 30+ times, this adds up!



The C6 Corvette is a hybrid of two styles of front end radiator cooling flow - it is both "mouth breather" and "bottom breather", so this splitter has to accommodate both flow paths. And it does so rather well - we did not see any change in cooling efficiency with this splitter, and I was worried about that.

Normally on a purpose built track-only car you block the lower inlet, re-route all radiator flow to a front "mouth breather", and redesign all of the radiator ducting to make this work better. Which is a lot of work - this GSPEED cooling kit for the C5 starts at nearly $5800 and includes a plywood splitter.



The sad fact is, because it blocks the brake cooling, this carbon splitter should not be used by track folks - unless you are willing to completely redesign the brake cooling inlets. Zach here spent hours drilling holes and adding rivets to mount this piece, and it sure looks sexy, but the compromises to brake inlet ducts are real. I have some data from a later track test that will show how this raised front rotor temps by +250 deg F - for now, pulling this off was the right change. We might go back and re-add this at some later point but not until we really need a touch of front downforce or show car cred.

PANAVISE BASE + RAM PHONE / CAMERA / AIM HOLDER

The 2005 era C6 Corvette's interior has aged a bit, and one of the things it is missing for today's consumer electronics is a Apple /Android Carplay style radio. In place of that (and one of these is in the plans), it still needs a decent spot to mount a smart phone - and if you have followed my build threads you will recognize the giant RAM quick release 3-axis phone holder that I have in literally every vehicle I drive.



For the first 4 track tests I was using a suction cup mounts for the AiM SOLO DL lap timer / data logger, another for the Sony vidcam, and a third for the RoadKeeper dual 1080P camera system. All of these suction cup mounted devices were blocking my view forward a bit, so it was time to address this.



Jason here at Vorshlag turned me onto PanaVise, a company who's been around for ages (with the same 1998 era website) that make these little steel brackets that bolt into specific car and truck models without cutting or drilling. They tend to snake them between trim panels and radios, and bolt to a rigid dash mount for the radio. Brad installed the C6 Corvette version of the PanaVise bracket + a 4-bolt RAM 1" ball base, which the PanaVise is made for.



Ever since this late July 2021 install I have used this 1" RAM ball mount with a 6" arm to hold either the RAM phone holder (above left) or the AiM SOLO bracket (above right), which de-clutters the windshield view by one device. I have also settled on one main video camera (the dual vidcam RoadKeeper) for most of these events, because I scratched the lens on the Sony. I've since lost about 50% of the video taken with the RK camera, and will be moving back to the Sony soon. Long story there.

"LOWER BITE" REAR PADS (FAIL) & OTHER STOCK ABS TRICKS / TESTING

So by this point in July 2021 I'm really starting to hate this car, simply because we cannot even get a decent "baseline" lap with the stock suspension, upgraded 275mm R-S4 tires, and Z51 brakes. Why? Well ever since we added the R-S4 tires the rear brakes keep locking up - it happens on the street and into the entry of any corner that involves braking. If you exceed 1.0g braking force on any stop, the rears lock (for a long second), which makes the car violently tail happy, and if you don't let off the brakes the rear will come around. All I am doing on track is managing the rear lockup, not focusing on "driving".

One of the many "fixes" we heard from many "GM ABS Excusers" was that you cannot run a rear brake pad with any "bite" or higher friction coefficient in the rear. So after 2 track tests with the rather mild R10 compound G-LOC rear pads (coupled with R12 fronts) we swapped in these "Brake Best" parts store branded ceramic ultra quiet pads in the rear.



Of course this didn't fix a damned thing and the rear lockup continued. We left those on the car in for the next few track days as well as a half dozen ABS street tests - where we altered rear tire height, front tire grip levels, rear grip levels, etc. We spent hours and hours changing variables and doing street tests - but the rear brakes kept locking at anything higher than 1.0g stops (the rears would "only" lock for about one second, then unlock, then re-lock, and slowly pulse until you came to a stop). The only "fix" was to swap in the original 500 TW craptastic rear tires, which cannot generate enough rear grip to get into this "bad programming" area.

TRACK TEST #4 - AUGUST 20, 2021

I did track test #4 with these low bite rear pads and the harder compound, stock 500TW rear tires, and it DID make the rear brakes stop locking - but the rear grip and balance were so far off that it slowed down from our baseline lap on a totally stock C6!



The track performance was complete and total garbage - and nobody likes a car that slows down from stock, not after we had a 2.5 sec drop in test #2.



At this August track test I used some one-time-use temp strips on the power steering line and alternator showing the fluid getting VERY hot, and with more seepage at the rag / cap. The alternator also gets pretty warm, but so far that isn't causing any issues.



After test #4 (August 2021) we didn't get back on track with functional Mk60 ABS until March of 2022 - and I forgot to swap the G-LOC rear pads back in. Well the soft pads didn't last 3 sessions, and actually ruined one of my track tests (Test #6). Lesson learned there - don't listen to "the internets" and use the correct track pads at all times, unless you want to go very slow. There is no good "fix" for poor performing ABS. And yes, the ABS programming on this base model car was likely worse than most Z51 / Z06 / GS C6 cars, which I have driven on track without this issue (but I can still Ice Mode all of those in a parking lot.)

These brake locking issues occupied too much shop and testing time, and ruined months of work spent chasing ABS fixes. It was time to do something serious to correct this, and we started with an ABS swap right after test #4.

Z06 POWER STEERING COOLER

After almost all track tests I noticed noisy power steering pump and some fluid around the cap, which we had swapped out with Motul ATF ester based fluids early on. There literally isn't better fluid to try, so it was time to look at a better power steering cooler.



We found an OEM replacement cooler complete with lines from a GM supplier and it was about $200, if my memory serves me. Much easier than building an elaborate cooler, changing all of the lines, etc. So during one of our many ABS tests in October 2021 Brad swapped in the C6 Z06's finned power steering cooler in place of the base models' hard line "loop".



It all fit and plumbing was a breeze - you never get this lucky in most cars, but this is one of several Z06 upgrades we would do to this car over time. Brad said he had to tap the two mounting holes on the cradle to fit the brackets, but the holes were there. Ever since doing this upgrade the power steering noise, measured heat, and fluid seepage was way better.

S550 MUSTANG ABS SWAP (FAIL)

In October of 2021 we brought the C6 into the shop and started an ABS swap using a junkyard sourced 2015 Mustang GT brick, shown below. I wanted to try this swap on a car due to the exceptionally good braking I've seen in S550 Mustangs AND the low parts cost. The Ford ABS bricks tend to be sold for $90-150 complete, with all of the hydraulics, pigtails, and the computer. There are no external sensors needed.

I will fully admit now that this ABS swap was a bad idea - but at the time, I had some incorrect information that said the 2015+ Mustang system was a valid candidate for an ABS swap. Well it might indeed be - but not without a lot of CAN trickery.



To be honest we have been able to swap the earlier 2011-14 "S197" Mustang ABS brick into a C5, and it has the best braking of any Corvette I have ever driven. It took a LOT of work and a special Ford Racing computer to make it function without external CAN inputs. I had hoped the newer S550 ABS would work the same way, but without the special Ford computer, it was a dead end.



But I still had Brad waste dozens of hours making a custom brackets to mount the S550 ABS brick into the C6, then plumb it into the rest of the system.



Long story short, once it was wired up and proven not to work, and I had since learned better information from a racer more familiar with S550 Mustang's without CAN wiring who told me this was a dead end - there's not a path to an ABS swap with this brick at this time. I'm convinced with enough effort we could make it work, but we had just completed another BMW Mk60 ABS swap in another car, so at a certain point it was time to "punt" and go down a path that had more support for ABS swapping.



All of that time spent wasn't a complete loss (just mostly a loss) - as we did learn how to make the car start with the GM ABS disconnected. We documented it above with some good graphics and pictures, which we will include into a separate ABS swap thread on our forum, to act as a knowledge base for future use. Why my own forum? Because it has been up for over 20 years, as has my Smugmug gallery (50K images+). I trust it better than some random forum or free photo hosting site.

BMW MK60 ABS SWAP

I let the C6 sit from late October '21 to early February '22, because I was just disgusted with how badly the brakes were working, then the S550 ABS swap being a dead end. But after we had some room in the shop we brought the C6 back in for another go. I had been purchasing the parts needed to do the BMW E46 M3 Mk60 ABS swap on this car.



The components you need include the correct year / model of Mk60 ABS brick, two external pressure sensors, and a yaw sensor (the later S197/S550 ABS systems have all of these within the ABS brick). There's about $800-1000 in parts from the right sources.



You also need a stand-alone wiring harness made for this swap, which right now costs about $1200 from sources like Racing Harness Technologies (who we have used several times). RHT can also supply the pressure sensor adapters like the ones above, which is $150 but could be higher (they come from Germany and take many weeks to arrive).



We had to make a pedal switch to let the system know you are engaging the brakes. And of course this C6 wo9uld need different wheel speed sensors (active). More about that in the section below. Brad built the bracket above to mount the Painless Performance brake pedal switch.



The brake pedal actuation switch doubles up with the OEM clutch switch (top left) and the yaw sensor has to be mounted in a very specific orientation - which required another custom bracket.



continued below

[Fair!]

Project Update for June 16, 2022: The last forum build thread update here only got us thorough May of 2021, so this is be big "catch up" post that covers our C6 work from May 2021 to April 2022. So much work has been done to this narrow body C6 since then - a seat upgrade, harness bar, 6-point harnesses, an MCS coilover install, ABS testing, two ABS swaps (one of which worked), a carbon front lip, baseline dyno run, wheel testing, brake pad swaps, alignments, wheel hub changes - as well as five track tests to verify all of these changes!



As you will see, there are several things we attempted in this series of tasks that did not work - and I label these in the headers of each section as FAILS. There were both wins and few fails on the C6 over the course of the last year, and while I'm not proud of choosing to go down the wrong paths, I don't hide my mistakes. As always, we try to share what works and also what does NOT work, so that you don't have to learn the lessons we did if you attempt to replicate this work on a similar car.



But we did a number of modifications that were solid WINS, which helped contribute to FIVE SECONDS of lap time improvement from our initial baseline lap times, all from the work shown here (and we have gone 2 more seconds quicker since, which I will show next time). We try to only add ONE VARIABLE per track test outing so that we can isolate what works and how time much it is worth. Who else does this level of testing - we're at 10 track tests to date - and shares that with everyone? If you can point them out to me, I'll buy them a beer.

TRACK TEST #3 - MAY 27, 2021

As I mentioned at the end of the last post, the "performance alignment" we had done at a local shop really jacked this car up - and Track Test #3 was the first time I drove it like this, and at MSR Cresson on their 1.7 CCW course as always. We always strive to test on the same track configuration / same driver / same tires / same conditions.



I brought the C6 out a Thursday in May, with weather at 79F and cloudy, and the track surface had been scraped recently to remove some bumps from a recent repave (it has since been paved again). A little rain the night before left a small wet spot on track entering Turn 9, but nothing impacting lap times.



This was the first time we ran the car with the upgraded Z51 brakes with new calipers and rotors, the same G-LOC pads from before (R12/R10), the new tow hooks, and the "performance alignment" with -2.5 deg camber up front, -1.0 out back. The rear toe out was not obvious, and of course it WRECKED the handling - and lap times suffered.



I was a solid 1/2 sec slower than test #2, as both the rear brake lockup issue was still bad and the rear toe out issue made the handling just TRASH. Ran the same 275mm Hankook RS-4 tires on 19x10" wheels. I thought the ABS was all of the issue here, but it was only partly to blame (but still a major hiccup).



Extremely frustrating day at the track - going slower while fighting both handling and brake issues. After many laps going nowhere I loaded up and brought the C6 back to the shop - we had a lot of work to do.

CORBEAU SEAT INSTALL + CUSTOM BRACKETS

This seat upgrade was eluded to in the last two updates, and we tackled this over early May through late July 2021. If that seems like a long time - it is. And we didn't install the second seat (passenger side) until June of 2022. This upgrade isn't exactly a "win", but it wasn't quite a fail either. I'm not going to release this seat bracket for sale yet because 1) it will ONLY work on THIS model of seat, 2) I'm not sure we've found every inch of room there is, and 3) I don't know if this is a viable product to release. I will explain more below.



Part of the initial delay on the first seat was because we designed and built several iterations of a bracket assembly for this "bottom mount" seat and slider, trying to gain both headroom and rearward travel in the cramped C6 cockpit (the C4-C7 Corvettes are all very small inside) while keeping the overall seating position the same as stock. To be honest, the seating position we have now is less than perfect for anyone over 6' tall with this bracket + slider setup.



The Corbeau seat itself is a VERY nice upgrade over the base C6 or even the C6 Z06 seats we have on hand. They have a lot more leg support, shoulder and rib support, and shoulder harness pass-thrus in the seat back. And the shoulder harness slots are above the top of my shoulders, which was a good thing - not all seats fit taller torsos. There is also a path for the lap belts but not a pass-thru for a 5/6/7 point harness anti-sub straps. The covering comes in several styles and stitching colors (not my favorite but she likes it!) and we ordered the driver's seat with an optional seat heater - its good for my lower back and Amy loves these things (we didn't hook that up until June 2022).



Like most Corvettes this 2006 base model came with a power driver's side (45.6 lbs) and a manual sliding passenger's side seat (35.8 lbs). The Corbeau is slightly lighter 28.7 lbs, without the slider or our final seat bracket. And while the Corbeau is considerably more supportive, with the external bracket and slider we had to build we did not gain any additional headroom - which was one of my major goals.



We started with the flat style seat base bracket design we have done for the C5 and other cars, but with this bottom mount seat we quickly realized we could never get the base tilted back enough to fit correctly in this chassis. Side mount racing buckets can be adjusted for tilt in the side brackets - not an option here (we needed about 7.5 deg of base tilt to match the stock seating position). Even with the "OEM style" brackets we started mocking up it visually it looked like the Corbeau would be shorter in height, but that was misleading.



After literally three months of tweaks we locked down the "final" design and put the driver's seat into the car. These went in raw steel and we made another set for the passenger side, that was eventually powder coated.



To keep the stack up height to a minimum we made the brackets separate front and back assemblies, which we CNC plasma cut in minutes, bent to shape, and TIG welded. And since this was going to be a dual purpose car we wanted to include harness attachments for 6-point belts as well as the OEM 3-point seat belts. We also ordered these Airbag Simulators (seat sensors) from Vetteworks Motorsports, which should keep the airbags working and the lights on the dash off. Plug these in BEFORE you turn the key on during your seat install.



Again, with the seat installed with our brackets AND a slider it sat a little higher than the stock seat, and a bit too far forward, due to the OEM brackets and slider being much shorter and sort of built into the bottom of the seat (the height efficiency is good). Our "anchor shelf" for the clip in harness anchors on the back of the bracket is keeping the seat from sliding back about an inch. I've been looking at this for 8 months now and still want to chase down a few other tweaks.



We also didn't save much weight with our Corbeau seat + slider + bottom brackets (40.9 lbs), vs the stock power seat (45.6 lbs) or manual seat (35.5 lbs). But for a tilt back seat with all of the bracket mounts for the 6-points it isn't bad. This design was a pretty "big ask" - to improve on the height of the stock seat using a bottom mount tilting aftermarket seat AND keep a slider AND add the additional 4 harness mounts. What we have now is not ideal, but the seats themselves DO feel really good and support so much better than the stock seats it is worth the less than perfect position - for now.

HARNESS BAR INSTALL

This upgrade is an unusual one for us - adding a "harness bar". Normally I am one to preach the benefits 4-point roll bars, for racing harness shoulder strap mounting AND rollover protection. But here, in the already tight confines of the C6 cabin with full interior, there's really not sufficient room for that - in my humble opinion.



The main steel structure of the base C6 is hydro-formed steel tubing, and that goes into the roof's "main hoop", shown above on a "naked" C6 Z06 chassis (which is aluminum). I feel that the factory "main hoop" structure of the C5/C6/C7 is adequate in 99% of rollover situations (which I have yet to experience in tens of thousands of track miles over 34 years of doing this). For a Wheel to Wheel car, of course you need a cage. And for not tall drivers that don't mind cutting up their Corvette, sure, get a roll bar. For the goals we have on THIS car, a harness bar is adequate.



I try to set the best example with my personal safety gear in whatever I am driving on track, and you will see me even on the hottest days wearing 3-layer SFI fire suit, the best helmets, HANs and more. But I'm not some "safety nazi" that says anyone "who tracks their car without a cage will die!" like some. There's always a balance, and only you can know your needs with respect to personal safety, the tracks you run at, etc.



Like many Corvette track rats we chose the Brey-Krause harness bar for the C6. This is a hoss unit and they are a very trusted name in the industry. The images above show the relatively simple steps needed to mount their anchors to the rollover hoop, then the hole trimming needed for the interior panels (if you reinstall those).


With the interior panels in place this harness bar looks right at home, and still allows access to the full rear cabin storage area. We left the carpet out once the MCS coilovers went in, but I will talk about that in a later section.

SAFECRAFT 6-POINT HARNESS INSTALL

With the harness bar installed and our lower seat brackets adding the 4 lower anchor points for clip-in harnesses (laps and anti-subs), it was time to choose the racing harness brand and style.



For many years we have been selling and using Schroth harnesses exclusively, but through a racing relationship that Tim here had with another Pro racer, we have started using Safecraft harnesses and nets. These are really and truly designed by a racer for other racers, and the feel of the buckles, the releases, the tensioners and straps is all "next level". I ordered these in red (of course!) and these use a hybrid 2" upper and 3" lower shoulder harness strap with 2" lap belts.



Installing the lap belts and anti-sub belts isn't easy on any of these composite cars, simply because there isn't much floor structure to bolt to or room behind the seat to place the anchors. We incorporated the anti-submarine and lap belt anchors into the lower / rear seat bracket portion, which again - cost us some rear seat slider travel. But the anchors are solid and work fine. The anti-sub portion slips between the lower and back portions of the tilt back seat and you sit on the harness and bring it up around your crotch. With a proper hole in the base of the seat you don't have to do that, but this is a compromised street/track seat - as are all tilt back seats.



How you wrap the belts around the harness bar matters - see the image above left, which should match the NASA/SCCA General Competition rulebooks. Again, without holes in the seat back it is nearly impossible to use harnesses, and GM didn't start making "track worthy" seat options until the C7 model. This upgrade is better than nothing, but not as good as a fixed back racing seat. And yet we can still use the 3-point retractable OEM belts.



Driving on the street with the 3-point stock belts is fine, and driving on track with proper 6-point harnesses is better than fine - but not yet perfect. We'll keep looking for that last inch of rearward travel and height, but it might not be there with a bottom mount tilting aftermarket seat. Stay tuned for more.

JONGBLOED WHEEL ORDERING & TEST FIT

Early on in this build I started making plans on fitting the widest tire and wheel package possible for a narrow body C6. Nobody ever runs these cars and I wanted to see how far we could push it with the stock fenders.



On a widebody C6 we've spec'd and built many sets of 1-piece 18x12 / 18x13 wheels and 335 / 345 tires, which is a tight fit but they work (some rubbing up front inboard) and makes MASSIVE grip. I knew we'd not get to those widths but I wanted to see how far we could push it. As I have preached for 30+ years, tires are almost EVERYTHING when it comes to autocross and track performance, and you can NEVER have "too much tire". We've proven this time and again on so many cars and all power levels. The C5 below left is one I have tracked and autocrossed many times and on the 18x12/13" Forgestar wheels and the 335/345 Hoosiers is is unbeaten in autocross across dozens of events.



On the same wheels and the 315mm Yokohama A052 street tires above it recently set Fastest Time of Day, over some tight competition - with only 425 whp in a tight parking lot! The FRS above right is our 2013 that we documented here with the same "make a change / track test" scientific method. The change from 215mm to 315mm tires was the single biggest change we ever made to that car on track, dropping 2.5 sec at the same MSR Cresson 1.7 CCW course.



Our two sets of 19x10" wheels were done to give us a "control set" to use across many track tests (9 so far) and the 275/35R19 Hankook R-S4 tire is very consistent over many laps also (the image above left is with a 295/35R19 Hoosier R7, which we mounted later - but haven't gotten a good lap on yet). We knew that 275 Hankook tire would hold back the car's on-track performance, and we wanted to be ready for whatever tire we could jump to beyond that little 275 for time trial or whatever competition.



In march of 2021 - before we had even received the first set of 19x10" wheels from TireRack - Jason measured the stock wheels and determined the maximum wheel we could fit, theoretically. Again, the aftermarket was not pushing the narrow body as far as we had hoped, so we "went for it" and came up with 18x11" front and 18x12" wheel specs that were "max fitments".



Normally this is where you'd see me talking about some custom spec'd Forgestar wheel... but their wheel blanks could not accommodate the massive inboard offsets needed to fit these sizes to a narrow body C6. So it was time for a 3-piece wheel, and we had been in talks with Jongbloed for many years - now was the time to get a set to test out.

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[Fair!]

continued from above

FRONT & REAR TOW HOOK DESIGNS

While the front nose was off I pulled engineers Zach & Myles into the C6 project to develop some new, bolt-on front and rear tow hooks for the steel framed C6. Sure, we make tow hooks for a number of cars, but why make these for such a "mature" Corvette model like the C6 (which has been out since 2005)? Well the offerings we have seen from others aren't... great.



In 2020 we made some unique and new tow hook designs for the C5 Corvette (shown above) that were very far from a "copycat / me too" design, and they have sold very well. We looked at the existing C6 offerings and came to the same conclusion - we need to make Vorshlag versions. This is another reason why we bought this car - product development, when it made sense.



Like our C5 front tow hook design, this steel framed C6 front tow hook mounts between the lower radiator support and the frame rail. Our C6 design also has a "tab" that is bent up and "pushes" on the back of the bumper beam when the car is towed forward from this point. The tow hook has a bend down, then then passes through an unused section of the lower grill - which we add a slot to some plastic (see above right) for the pass through.



I have personally pulled this C6 into and out of our trailer a dozen times with this front hook - I'd confidently have a tow truck driver pull it up onto a flat bed from here. It is VERY substantial.



Out back our crew removed the black plastic lower valance and we took a look at how we wanted to mount the rear tow hook. Like all of our designs we never want to make a customer cut through painted body panels to install the hook, but the black plastic bits are fair game.



Like the front, our C6 rear tow hook has a 2.0" diameter hole and is made from 3/16" plate steel, which we CNC cut in-house. The rear frame rail and bumper beam have a height difference so we weld on a spacer to the hook where it touches the bumper. This hook bolts to the steel frame and bumper structures with 4 bolts. The lower black plastic valance needs to be slotted to allow the tow hook to pass through. Nice and clean, and removable.



Our prototype pieces shown that went onto our C6 were spray painted red, due to time constraints, but our production tow hooks are powder coated in gloss red for a long lasting finish. These are the strongest bolt-on tow hooks on the market and they have been selling well for the past year. We keep making our various tow hooks in ever larger batches and will keep expanding our designs to other car models over time.



Lastly, I had our crew modify an existing towing tie-down strap anchor point design into a a C5/C6 specific one. This 3/16" CNC cut plate steel part can be bolted onto the rear lower control arm / sway bar point at the rear subframe, as shown above. We are updating this design and will have it for sale soon, but the Tow Hooks have been selling for almost a year.



I have a pair of these on the back of our C6 and it makes strapping the car down in the trailer SO much easier now - just reach under the car, attach the hook end of the straps into the long slotted eyelets, and then anchor the rear. Easier than going through wheels or running an axle strap through the subframe, as I had been doing before.

TRACK TEST #3, MSR-C 1.7, MAY 27, 2021

I brought our narrow body C6 out to MSR on a Thursday member day to test this latest round of changes on their 1.7 mile CCW course. Weather was 79F and cloudy, and the track surface had been scraped and patched recently to repair some bumps in recent repaving work. A little rain the night before left a small wet spot on track entering Turn 9, but nothing impacting lap times.



Again, Project New Balance had a number of changes from Track Test #2, namely all new calipers and rotors (Z51 brakes), tow hooks, and a "performance alignment" (-2.5 deg camber up front, -1.0 out back) that we had a nearby shop perform on their laser alignment rack. We really needed more rear camber, as this could make for a slight imbalance in cornering, but we will address that the next time it is aligned. The alignment shop we used had never done a Corvette - and it turns out they made more than a few mistakes (more on that below!)



All told I was a solid 1/2 sec slower than test #2, with the rear brake lockup was no better than before, even with all new brake parts. I used the exact same 275mm Hankook RS-4 tires on 19x10" wheels and G-LOC R12/R10 brake pads. You can see my horrible, best lap here on YouTube.



This was a depressing day of testing, and I left the track in a totally foul mood. The rear brakes kept locking in all 1.0g stops, and I tried every braking technique known to man - the only way to manage it was to UNDER brake into every corner. Straight line brake, stay under 1.0g, and never trail brake. It was also twitchy as Hell - I've been doing this stuff for 35+ years and I cannot remember a car that was actively trying to kill me on track like this one.

THE GREAT MYSTERY - C6 LEFT UNBALANCED!

This third track test was the beginning of a downward spiral into me hating this car. I watched the videos from that track day and could not put my finger on why it was slower than test #2? It was the same tires, same brake pads, and similar conditions. In this test, plus track tests #4 and #5, it took everything I had in my 3+ decades of track experience to keep that car on track - and still went 0.6 sec slower! I spent months and two more track tests fighting this car before we had a EUREKA moment.



Yes, the ABS programming was garbage, and we eventually fixed that with a full Mk60 ABS swap (below) - but even then, the lap times still didn't improve; I never could beat track test #2's 1:26.2 time! Why???? I searched my brain, watched my videos and analyzed data, and it finally occurred to me. In track tests #3, #4, and #5 the car was super twitchy, mid corner, and would never take a set. Sometimes when you are stumped you need to step back and CHECK THE BASICS.



We didn't make the lap times worse with the Z51 brakes - the alignment did. The shop who did the "performance alignment" on this car was not at all skilled at motorsports alignments. They have screwed up every alignment we have taken them, badly, and we quit using them long ago. Sure, we noted the lack of rear camber after looking at their work sheet, sure, but we neglected to CHECK THEIR WORK first hand.

It wasn't until March 2022 when Brad was installing the MCS coilovers that he found something. I always insist that any car getting major suspension changes go through a "baseline measurement" session before the work, then another after. We check ride height, camber, and toe at each wheel - before and after. And that is when Brad noticed that the alignment shop had REVERSED my written rear toe request... they had put 3/16" of TOE OUT in the back instead of 3/16" of toe in!

Which explains why the car was so twitchy in corners and would never "take a set" after the turn-in phase of the corner. This is why the car kept getting slower and was so hard to drive. Sure, the lack of ABS function made turn-in challenging, but this was a mid-corner phase oversteer/unbalanced setup. Dumb mistake that I should have known to check. I'm mad at myself more than anyone else. How did I miss this??



This alignment mistake was unfortunate and wasted a lot of time on this project - we would have installed the MCS dampers a half a year ago if the car would have just... progressed. The piss poor lap times kept making me wait, stalling out the project, and it sat in storage for months while we worked on other projects. We kept going down the ABS rabbit hole and finally fixed that, but it was still slow and twitchy on track afterwards. That's when I knew it had to be something else. The wacky alignment was the problem for so long, but it was impossible to even see that small amount of rear toe out visually - but boy did it impact the handling!

WHAT'S NEXT?

There is much more to share to cover the work we completed from late May of 2021, but that alignment revelation came only recently and it impacted the next many months of work and two more track tests. I am going back to the track later this week, with a proper alignment scheduled on a rack at a real motorsports shop that understands the importance of rear toe!



Until then I will save the coverage of all of the other modification work we did in late 2021 and into 2022 for next time. That will include the new seat brackets / seat install, harness bar, harnesses, Mk60 ABS (plus another aborted ABS install), big wheel testing, and more.

Thanks for reading!

[Fair!]

Project Update for April 11, 2022: It has been an eternity since I updated this project build thread - eleven months! - but the shop has been super slammed and I am behind on all of my forum build thread updates, videos, blog posts, and the rest. Since May of 2021 we have done three more track tests in this Corvette, following lots of suspension, brake, and safety upgrades. Since last April we have upgraded the base brakes it to Z51 spec, swapped in a Mk60 ABS system, swapped in new hubs and studs, upgraded to a massive aluminum radiator, made custom seat brackets, added aftermarket seats, added a harness bar and harnesses, installed a carbon splitter lip, upgraded the power steering cooler, performed 9 ABS tests, then swapped in MCS remote double adjustable coilovers. Whew!



The stock braking system fought us for most of the last year, and we often tried things that did not work - some of it from "conventional internet advice", then other things we tried on our own. Massive changes were made, with more still to come.



In addition to all of these changes and upgrades, one stupid mistake slipped through - which changed the "balance" in Project New Balance, and handicapped lap times on track tests #3 through #5. Live and learn, I guess. Over several months of work many hundreds of pictures and videos were taken, and I want to share that with you - but it will take several forum installments to get all of that published. Each one of these forum updates takes me 6-8 hours to write & edit, plus many more hours of photo and video editing. Please be patient as I try to dig out of a massive "forum post" backlog on this project and a half dozen others I try to chronicle. We will share all we have learned, the good so keep tuning in. Let's get started!

BRAKE UPGRADE - JL9 (BASE) TO J55 (Z51)

This narrow body C6 had the worst possible brakes of many offered on the C6 from 2005-2014, and we aimed to make the next logical upgrade - to the Z51 option's "J55" brakes (we will just call them Z51 brakes to make it simpler). I purchased new rotors from Raybestos and calipers from Centric and AC Delco. Strangely there was only one front Z51 front caliper available from Rock Auto at the time, but the calipers were identical on JL9 to Z51 - the only change was in the Z51 brackets, which I found on RA also. These move the same caliper "out" to work with the larger diameter rotors.



We looked at LOTS of other brake upgrade options before going this Z51 route, and honestly the "Z51 upgrade kit" I found on eBay (below left) might have easier - but I still wanted fresh calipers. I also looked at countless other options including C6 Grand Sport/Z06 brakes, AP brakes, Wilwood brakes, and more. I wasted several hours and stewed on this decision for days, but ultimately I went with the budget "RockAuto" Z51 upgrade - to show that maybe, just maybe - you don't need to spend several thousand bucks to make a Corvette stop. This is a rather light car (3100) compared to the normal 3600 pound street car Mustangs we build.



The JL9 option code included dainty little rotors on both ends that we replaced with the larger OEM spec Z51 units, shown below. The Z51 rotors were not only larger in diameter, they were cross drilled. Now I wouldn't have bought drilled rotors, but that is how most of the replacements come, and how the factory did it. Of course you don't NEED cross drilled rotors, as it is simply a holdover from poor brake pad techniques (degassing) from the 1980s, and the OEM's did them for decades longer because it "looked cool".



This Z51 upgrade was done in May 2021 when we were still chasing the weird brake bias / rear lockup issues on the car. We'd only done the first two track tests and were hoping we could "trick" the known-to-suck GM Anti-lock Brake System programming into... sucking less. Lots of suggestions were made online about brake pad compounds, tire heights, rotor sizes - some of the many things were known to trip up the factory ABS. We tested all of those and more, and none of them fixed THIS particular car, which had serious rear lockup unless we crippled the grip level to 500 treadware tires (I will cover much of this testing in a later forum installment).



As hot as we got the brakes in the first track test, as poorly as they worked, and as old as these parts were, I felt it was a good idea to replace the old calipers and rotors. And I had hoped to get the braking to work as well as it had on our 2005 Z51, which I autocrossed several times and never had it lock the rear brakes up. So I chased down new PBR twin piston front calipers and the mating Z51 caliper brackets, which spaced them "up" to deal with the larger diameter rotors.



Now the larger brakes would come with a weight penalty, but that is to be expected. The Raybestos branded 13.4" dia Z51 fronts were 23.3 pounds and the (admittedly worn) JL9 12.8" dia rotors were 19.6, for an increase of about 7 pounds for both fronts.



The delta on the rear rotors was worse because the diameter jump was larger, going from 12.0" dia to 13.0", and the weight jumped from 15.0 to 20.7 pounds, a nearly 11 pound increase. But more importantly, this larger diameter change would likely make the rear bias issues worse - and it did, once we tested on track. We needed to ditch this base car's crappy ABS in any case, which we did (and I'll show next time). After the Mk60 ABS swap the brakes work GREAT!



The front "upgrade" was pretty simple. Remove the caliper and bracket, swap to the bigger rotors, then the new Z51 spec brackets went on, then the calipers and pads. On one side we re-used the base caliper temporarily, simply because none were available at the time. This was swapped out about a month later and had zero effect on performance.



The rear was the same, only you might have to retract the rear parking brake drum brake shoes to get the old rotor off. There was one new hub on this car, changed by the prior owner right before we bought the car. The Z51 rear brakes were installed without issue and the same G-LOC pads (R12 front / R10 rear) were reinstalled.

REAR FENDER LINER REPLACEMENT



A seemingly small item, the left rear fender liner was all busted to hell on this car when I bought it. I think a previous owner had a blowout and it tore this liner up, and it had some extra screws and "zip tie surgery" holding it together. I found a good one on eBay for $68 and ordered it (it would have been a lot more and many pieces to get it from GM.)



The rear fender liner is a larger assembly and includes the factory rear brake cooling within it. When Brad was doing the brake upgrades he swapped in this used but good fender liner and replaced the old busted unit.



After that was installed (above left), the replacement front fender liner piece I found on RockAuto (above right) was installed on the left front as well. Now all of the liners are good.

COOLING SYSTEM UPGRADES & REPAIRS

One upgrade that goes with virtually every track-centric build is a larger and more efficient radiator. When the OEM unit has plastic we replace it with an all aluminum unit, too. We normally look at Mishimoto / CSF for some cars, but when it comes to Corvettes we have used one brand and had perfect success: DeWitts.



The factory single core aluminum/plastic unit in this 2006 model car was ~16 years old at this point, and plastic parts heated to 250F all the time don't last forever. The massive, all aluminum DeWitts drop-in unit was purchased to replace it. The core thickness difference is shown below - it is massive. We have successfully used these in C5s before so it wasn't a tough choice getting one for our C6, but it wasn't an inexpensive upgrade.



Removal of the old unit starts in the engine bay from the top, but we had some other damage that needed to be repaired and the entire front bumper cover was removed for that step.



The lower radiator support on all C5 and C6 models is a fabricated aluminum structure - and it is the lowest thing on the car. With an aggressively over-lowered front ride height, this car's lower support was smashed before we bought it. This is common and the aftermarket factory replacements are not expensive. The plastic bits that attach to this were holding many broken pieces together on one side.



The replacement was raw aluminum, and we didn't bother painting it. As we have seen before these low cost replacements tend to fit well and include all of the factory installed riv-nuts to attach all of the lower bits and pieces. Brad swapped that on when doing the Z51 brake upgrades and the cooling system work.



All new radiator hoses and a new 205?F thermostat were installed at the same time as the DeWitts radiator upgrade and lower support work went in.



Since it is a part of the pressurized cooling system, the factory remote reservoir and radiator cap were replaced as well. I had bought one for my truck at the same time, so that's the second one in the picture above left.



With essentially a brand new cooling system and a massive radiator upgrade, I felt confident that the coolant temps wouldn't be a worry for future track test - and they have not been. An ounce of prevention is indeed worth a pound of cure.

FRONT AIR DAM REPLACEMENT

The C6 has a cooling system that is a "bottom breather" - meaning, much of the airflow for the radiator comes from under the front lip of the car. The lower grill feeds the ducting for the radiator with a section at the top that feeds the air cleaner. As you can see the front brake ducts are also under the car.




GM utilized a lower air dam made of three plastic pieces that kept the air going to the radiator (and brake ducts) instead of underneath the car, reducing lift. With the ultra low front ride height somebody dialed into this car the air dam took a LOT of damage and needed to be replaced.



I found the GM replacement piece online for a good price and Brad installed those when he wrapped up the cooling system work. This is technically part of the cooling system so it was a good time to do this.

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[Ando]

Terry and Vorshlag Team,
A couple of observations from corvette track cars over the years, I know you guys know most of this stuff already, but it bears repeating....

Suspension Bushings are crazy soft on the Vette and only poorly control camber especially once you get a really good tire on there. Delrin kits are available from a couple of suppliers and make a noticeable improvement in feel and control of the contact patch. Bearing kits are available but expensive. Polyurethane is also available, but with the obvious drawbacks....

Corvette Control Arm camber eccentrics are notorious for slipping, especially on good tires or when torqued to only the factory torque spec like an alignment shop is likely to do... Either crank down on those things or better yet switch to a "camber plate" system that locks out the lower bolts and adjusts alignment using shims on your upper control arms. Added benefit of making alignment adjustments with minimal toe change. A slipped eccentric will really ruin your day....

The oem single sided C clamp type brake calipers will always taper the pads, necessitating flips and rotations, but eventually the soft aluminum calipers will actually spread and wear very unevenly from top to bottom. The sooner you switch to a fixed caliper system the sooner you can save on pad costs. There are a few fixed caliper systems that use the stock cheap rotors, allowing for frequent inexpensive rotor changes.

Corvette brake force is electronically distributed. It seems to have a heavy natural rear bias and electronically reduces rear pressure. This is just one more aspect of the overall weirdness of gm brake systems, but there might be improvements to be made by upgrading only the front to add some natural bias especially with a square wheel set up.

The clutch throwout bearing slave system holds a ton of heat and cooks the fluid, suck out and refill the reservoir often. The oem clutch master cylinder has a lot of problems, adapting to an after market tilton or similar removes the return spring system and makes for a more natural clutch feel and to prevent a sticking clutch pedal.

Like with your engine oil, replace the power steering fluid with a quality ester based synthetic like Redline, or maybe Motul makes one?

Vent the hood to get enough airflow, add ducting to the front brakes, add oil cooling, you can see heat is already going to be an issue when the temps go up, after that start watching your trans temps.


Finally Thanks for all the great content and posts!

[Fair!]

continued from above

Since this was a Sunday and we had seen so much traffic on track at the last member day we aimed to get there around 11:30, hoping to get on track before the 12:30 lunch break. Which almost happened, but we got out on track at 12:30-1 pm and again in another session at 2:00-2:30 pm. Between Amy and I we made 23 hot laps this time, without any brake overheating issues. Now we still had brake problems, but that was all a rear lockup situation. That ABS was wigging out any time either of us braked over 1.0 g.



We saw accelerometer data of around 1.15g (both lateral and braking gs) but the rear tires would lock up quickly in stops over 1.0g, then the car tried to swap ends. Amy (a much smoother driver than me) saw the same issues, so we both had to dial back our braking considerably, especially when compared to other cars we have tracked in the past. Now we might have a sticky caliper piston, or some other mechanical issue - so we are preemptively changing ALL of the calipers and rotors in the next round of mods. I have felt Ice Mode / ABS issues on virtually every GM car I have ever driven on track, including multiple C4/5/6 Corvettes and 5th gen Camaros, so it might just be this issue.



The video above has more data channels from the CAN data stream, logged via the AiM Solo after I properly uploaded a new firmware versions specifically for the C6. Everything worked except the Steering Wheel Position Sensor. In fact this sensor often breaks on many C5 and C6 cars, so we think this happened - we got a "Service Active Handling" fault at both events. As always drove with both the traction control and active handling control systems turned off, as it is faster on virtually every OEM car than leaving the electronic nannies on.



We met our friend Jerry out at the track and I chased him for a bit in his C7 Z06, but he was several seconds a lap faster, so I didn't chase him long. It was supposed to rain all day but didn't, and the 63°F ambient temp was perfect. We even saw rainbows in the clouds.



This time we stuck around longer and drove in 2 different track sessions. My first stint was just 2 laps, to scrub the brand new tires and get them up to temp, and I quickly came in to let Amy bleed the tires down to 33F/31R hot. The understeer was still there but not as pronounced as on the 245/275 All Seasons. There was a LOT of traffic and I was one of the slower folks on track, so I had a lot of aborted fast laps to get out of people's way - and of course a few close calls where the rear tires locked into the big braking zones (T3 and T9 - see track map below). In my second stint in session 1 I made 5 laps and managed a 1:26.428. Then we swapped Amy in for 4 hot laps where I coached.

We had an hour to kill before our next session where we could go out and we relaxed a bit and Amy and I talked about her comfort level in the car. We made some seat position changes before going out again. Traffic was much lower in session 2 and I went out for an 8 lap stint, running two other 1.26.9 laps back to back. I had a high 1:25 lap on predictive timing while chasing Jerry's C7Z, but a 1.1g stop into T3 nearly sent me off track backwards, so I reset and went for one last blast the next lap - finding another couple of tenths with a 1:26.248 best.

Amy then went out next for a 5 lap stint where I didn't ride with her, and she had virtually zero traffic - which helped her get into a groove where she dropped TEN seconds from her best laps back on April 9th! She came in beaming, knowing that she was much faster this time. And more importantly, she had a lot of fun - which was the point of this C6 purchase: to get some track time while our other cars are being built and to have a ball doing it.



While the rear tire lock up issues were unnerving they were not completely unexpected. At least the G-LOC pads never got so hot that the fluid boiled and we never had a long pedal, always had good pad bite - but perhaps too much for this ABS systems. Not a huge problem, and if this persists after the next set of brake upgrades, we have another couple of ABS systems we can swap onto this car. Was hoping we could avoid that, we will see.

"INTERIM" WHEELS ORDERED (TWICE)

Remember the "one mistake" I mentioned in the 19x10 wheel and Hankook tire order we made after Track Test #1? Well it was the fact that I did NOT order black wheels, but that's what they sent. And I absolutely HATE black wheels - they disappear and you cannot see what they look like. Just a mass of black.



I mentioned this to my TR rep and he admitted the error, then sold me another set of these 19x10s in the correct silver color, above. Luckily these were still on closeout and again super inexpensive, plus at I got free shipping this time. I also found some TPMS sensors elsewhere and had the 275 Hankook tires swapped to these silver wheels after just that one event.



Not a great pic but it was raining all week and that's the best I have for now. Long term these will likely be the "street wheels" we use to drive around on, after these RS-4s have either worn out or heat cycled out. The "real" wheels we custom ordered 6 weeks ago are almost done, and those will be used exclusively for track/autocross use. More on that next time.



Meanwhile the ugly black wheels will now be getting a set of new Hoosier R7s, which I picked up for a song (old date codes, but stored inside and never mounted so they still have the mold release). The Hoosiers won't go on the car until we have the MCS coilovers on, and then we will test that setup with the 275 RS-4s first and the 295 Hoosiers on identical wheels on the same day. Just couldn't pass up this deal, and its more data in my long term 200TW vs R-compound tire lap comparison testing - which we did extensively for 2 seasons of NASA TT events in our 2018 Mustang in TT2 and TT3 (2018-2019).

LAP TIMES LIST RANKING AT MSR-C 1.7

Here is my "leader board" list for laps at Motorsport Ranch Cresson on their 1.7 mile CCW course, and the first two track tests on the C6 are shown ranked inside my videos/times for other cars I've driven here.




Love this track and have been coming here for 20 years. Their 1.7 mile course (see above) is relatively easy to learn, has a good mix of corners, and is short enough to not have a long out lap and in lap - making for more laps in a 30 minute session. This facility has had consistent paving from when they opened in 2000 until they repaved in 2021 - a month before the recent repave, NASA drivers were still setting new lap records on the "old" asphalt. Having driven before and after the repave, there is no significant change and lap times didn't change - not something you can say for most tracks over 2 plus decades of use.



We have used this course for setup and testing, and I personally have driven over 500 laps in many different cars here. With this much seat time at the same track I can drive fairly consistent laps, in the same conditions. In the past I have done as many as 15 track tests / competition weekends in a single year on this same 1.7 CCW configuration. MSR has 4 configurations: 1.7 CCW. 1.7 CW, 1.3 mile (see above) and the 3.1 mile layout (combines 1.7 and 1.3 together). We finally got a membership earlier in 2021 so we can do even more testing here. The only track I have more laps at is Eagles Canyon (above right), but they repaved recently and reconfigured (from 2.9 to 3.1 mile) about a year ago, so none of my old laps there are relevant to compare to for current testing. Plus their new 3.1 mile course is a bit long for a small number of laps driven in a given stint - with long out- and in-laps.



I keep this list updated of my best laps at this track in various cars I have driven, and put this list into most project build threads to show how a particular car is progressing, compared to other cars driven by the same driver - me. Why just my times? Well simply put it keeps the "driver variables" to a minimum.

I am not claiming to be a great driver by showing "my list" of laps only - far from it, I know I'm a hack - but I have driven 50+ cars at this track and have set 5 or 6 NASA Time Trial lap records here. As "terrible" of a driver as I may be, my laps here tend to be fairly consistent when the tires/brakes/traffic line up, often running multiple laps in a row in the same tenth of a second. That consistency can at least help show a progression of performance for a car over different rounds of modifications driven at different times, even if my times aren't the absolute best that a given car could theoretically do.

This list of laps shows a spread of times for a range of cars under similar conditions, with both 200TW and Hoosier race tires, as noted. Each time we add a new Track Test for this C6 I will add it in bold into this ranked lap time list:

• 2013 Scion FR-S, Baseline Stock Lap Time, 215mm tires (Test #1), 8/31/16: 1:31.90
• 2006 Corvette, Baseline Stock Lap Time, 245/275 all season tires (Test #1), 4/9/21: 1:28.743
• 2016 Focus RS, baseline stock laps, 235mm MPSS, 6/15/16: 1:27.40
• 2006 Corvette, G-LOC R12/R10 pads, 275 Hankook RS-4 tires (Test #2), 4/18/21: 1:26.248
• 2013 Scion FR-S, AST 5100s, camber, bars, BBK, "not fresh" 315mm Rival-S tires (Test #6), 8/25/18: 1:25.978
• 2001 BMW 330i, NASA TTD prepped, 216 whp, MCS coilovers, camber, 245 Hoosier R7, 3/12/17: 1:23.789
• 2016 Focus RS, coilovers and camber, 275mm RE-71R, (Test #4) 9/27/16: 1:23.658
• 2012 Corvette C6 Z06, Carbotech XP10/XP8 pads, 285/335 MPSS, perf alignment, 9/16/16: 1:22.63
• 2013 Camaro SS 1LE, 305 Hankook RS-3, Bilstein PSS, camber, seats, brake ducting, 430whp, 9/16/16: 1:22.56
• 1992 Corvette, NASA TTC prepped, LT1, 288 whp, stock shocks, Hyperco springs, 245 R7s, 3/13/16: 1:21.90
• 2017 Corvette Grand Sport, Z07 aero package, 285/335 MPSS, perf alignment, 9/16/16: 1:21.89
• 2018 Mustang GT, "sort of" TT3 prepped, 305 RE-71R street tires, 474 whp, 3/10/19: 1:20.348
• 2018 Mustang GT, "mostly" TT3 prepped, 315 Hoosier R7, 474 whp, 3/10/19: 1:19.2
• 2011 Mustang GT, NASA TT3 prepped, 335/345 Hoosier A7, 447 whp, aero, 3802 lbs, 3/9/14: 1:17.310

This C6 is actually a bit slower than we expected, when compared to the red target times above - a nearly stock C6 Z06 and a C7 GS Corvettes that I drove on the same day. Both the C6Z and C7 GS had performance alignments and much wider OEM tires, so that explains some of this deficit - but not all. In the next post we will have more lap testing on our C6, hopefully moving this car's best time up the leader board - eventually ahead of the Spec Miata track record! #LapTimesMatter

PERFORMANCE ALIGNMENT

This is something we recommend for anyone to do to their car BEFORE they ever go do their first track event in any given car. The goal for most unmodified cars you want to autocross or track is to add as much negative camber the stock adjustment range allows - because the stock suspension will allow a LOT more body roll than one with a modified suspension. And excess roll allows the tires to wear abnormally fast on the outer shoulders. Adding static negative camber will mitigate this, of course.


The first autocross in our 2018 GT shredded the OEM tires. Look at that roll! With coilovers/springs/camber it wore the tires GREAT

We had intended to add a Performance Alignment to this C6 between Track Tests 1 and 2, to show that as part of the lap time progression. Why wait? I wanted the Baseline Stock track test to be the absolute "stockest of stock" for this base model C6, and also why we did that one with the all season tires and random brake pads (but with good brake fluid and oil - I'm not suicidal). As you can see (below left) the C6 had tons of body roll, even on low grip 245/275 all season tires.



Well timing didn't work out for this to happen until after Track Test #2. Since we moved our shop "out to the country" in 2018 we have been looking for a place nearby with a proper laser alignment rack. We don't own one of these $75-100K alignment racks and it's unlikely we will - because they would never pay for themselves. In our best months we had maybe 3-4 cars aligned using a partner shop (that little use would never pay the note on these machines). At our last shop location we had a nearby shop with a really nice alignment rack and we would take cars there with a list of measurements we wanted. After a while we had trained their crew to do performance alignments to our specs. I was "breaking in a new shop" the week before Track Test #2...


As a test for a new nearby shop, I had taken my shop truck (above) to check out their abilities on a state of the art alignment rig, and they did a great job. They do 10-12 alignments per day, but on the only open slot we had for the C6 (the day before Track Test #2) they were slammed and couldn't fit us in, so we did BOTH first tests on the crappy stock alignment. That hurt lap times, for sure.



Looking at the car in stock form (above) we could see that the alignment was as Plain Jane as the rest of the car - it never had a performance alignment, and this is likely as it came from GM sixteen years ago. After we finally got the car aligned we can see the "before" settings were pretty bad: -0.6°/-0.8° camber front and -0.4°/-.6° camber rear. Oof...



They hit the marks we set for them, but it took them longer to do than they expected. These Corvettes require a lot of shimming on the front suspension to get the camber set. At least track test #3 (later this week!) will have some proper camber, and that alone will help lap times. We will likely dial in more rear camber on the next alignment as well (there are two mods planned in the future that will require new alignments).

WHAT'S NEXT?

We have a LOT of things ordered for future rounds of modifications and subsequent track tests. If I have to go to the track once a week to test all of these, well darn, I guess I will do it!



Brad is in the middle of swapping all of the calipers and rotors for the larger (and different hydraulic piston sized) Z51 bits, shown above. Also the DeWitt radiator, new hoses, lower radiator support (old one is smashed), and more. We should be back on track later this week to see if this makes for any changes in Test # 3.



There are more planned upgrade parts already here or en route, but those will be for later rounds of mods. The MCS dampers coupled with real spring rates should make a substantial change in handling - and might even help with the rear brake locking situation (old dampers and springs allowing too much rear rise/brake dive?) We will see in the next track test if the Z51 rear caliper hydraulic changes help that situation. We can always "dumb down" the rear brakes by swapping in some really crap rear pads, too. Stay tuned for more!

Thanks for reading,

Terry @ Vorshlag

[Fair!]

continued from above

TRACK TEST #1 APRIL 9, 2021 - STOCK BASELINE

With the initial maintenance items handled, some proper oil and brake fluid in the car, and with the C6 in otherwise sad stock form it was time to go to the track to get our Stock Baseline Laps in. This is the target lap we will try to improve on with this build. We utilized Motorsport Ranch in Cresson TX for this round of testing on a member day when they ran the 1.7 mile course in the CCW direction.

Event Gallery: https://vorshlag.smugmug.com/Racing-...mys-C6-040921/

I was hoping to get some laps in at ECR on the same stock configuration but our membership there might be delayed a bit. So we will use the MSR 1.7CCW to do all of our testing, for now. As I explain below in more detail I have over 500 laps on this layout over the past 2 decades and it works well as a test track, due to the layout, length, consistent surface condition, and my familiarity with this course.



Amy and I left for the track around 6:30 am and got there just after 8, with fairly light traffic for a Friday morning. We quickly unloaded the C6 then... realized we had outdated schedule info on when the first cars would go out on track. So we took the time waiting for the track to open to get two cameras installed, the AiM lap timer, then checking fluids and tire pressures. We went out with 31F/30R psi cold pressures - which turned out to be WAY too high.



We were there the same time as a lot of track friends with much cooler cars. I only barely remember seeing any of these cars out there when we were, as we had our hands full trying to keep this C6 on track while fighting brake fade and of course the REALLY poor stock seats (which were worse than I remembered).



We went out a bit early in the "8:30 am" sports car session and spent 34 minutes straight driving this car, swapping drivers on pit lane. We had some real concerns - with the brake pads overheating and the oil temps touched 275°F - but we were really watching oil pressure. The digital gauges on the C6 can only show one thing at a time, and while Amy was driving I was looking at that number closely under braking and in corners (by the next test I had enabled the CAN data to log this). I never saw oil pressure dip under 40 psi.



Click the image above to see the best lap on YouTube. Amy happened to be riding along on that, and I explain why below. Made for some hilarious in-car commentary! She was not having fun riding with me, but she took 6 hot laps when she drove (she is never a good "passenger" on track!) Our AiM DL was only setup to get the basic OBDII data - tachometer, Throttle Position Sensor, and a few other useless things (I had CAN data logging enabled for Track Test #2) plus the g-meter and GPS from onboard the AiM.



I went out alone for the first stint and the stock brake pads were VERY unhappy, and the 245/275mm all seasons were howling around every corner. I could overheat the brake pads pretty easily, so I had to baby them to get them to cool back down. So I adjusted my driving to not use as much braking - definitely an area we can improve upon for test #2. In my first stint I ran two 1:29.93 laps followed by a 1:29.67, a bit frustrating and very very slow. Amy ran 6 hard laps with me coaching and was finding time - but the brakes were not giving her any confidence. Then we hot swapped for 2 more hot laps with me driving and Amy riding right seat. Bleeding tire pressures down allowed me to drop a solid second from my first stint to a dismal 1:28.743 best lap.



We tested a new video camera along with the trusty Sony HDR-MV1, and the RoadKeeper dual 1080P vidcam was a roaring success. I will cover more of this in a review next time, but after 2 track events using it I am very happy with the video quality and the dual cameras is a nice feature. There are some quirks and cons, of course, but I will go over those in the review in my next Forum Build Thread Update.

I was only watching the oil pressure gauge while on track, as scrolling through two screens to see TPMS data is impossible. We stopped to check then bleed down the tire pressures after my first stint. Amy said the fronts and rears were at 45 psi after I came in! I had her bleed those down to 34F/33R psi for her stint, and we bled them down again at the next driver change - when I drove and she rode shotgun with me. Having tire pressures in the right range made a noticeable difference in grip, allowing me to drop nearly a full second in my last stint, even carrying a passenger.



Those lap times are painfully slow (you can see how they ranked in my "lap list" at the bottom of this post). Sure, both of our driving was pretty rusty, but I felt the rust "breaking loose" on my second stint. My last time on track was here in January of 2020. Amy's last time on track here was in 2018, and she never got into a good groove - when she's comfortable in the same car she's usually in the same second as me (and has NASA TT wins of her own). I tried to get her to go out again in a later session, but there was going to be an hour of waiting (open wheel cars and motorcycles each had 30 min sessions) and she was ready to go. The ineffective brake pads were just not confidence inspiring AT ALL, and I don't blame her. I sure didn't want to drive it like this any more!



The stopping performance on the random parts store pads was just BAD - two half-serious stops in a row would overheat them. As we swapped drivers in the pits there was smoke POURING off the front brakes (from the lack of airflow while stopped - they heat up). Next lap out the pedal would go to the floor on the first stop, so we had to make cool down laps at both the end and beginning of each stint.

REPAIRS AND UPGRADES - ROUND #1 MODS

Looking at the front tires after this event, I am surprised they weren't just shredded on the shoulders, as much as these things were howling and understeering badly. Turns out when you have rock hard 500 treadwear tires, they don't wear super fast. They also didn't make much grip!



This car had a mix Goodyear, Hankook and Michelin tires when we bought it, with that 30mm spread in front to rear widths (245/275) - which contributed to the serious understeer the car had (per the GM design - to make it safely understeer for the "lowest common denominator" random Corvette buyers). We needed something better - and now.

INTERIM WHEEL & TIRE UPGRADE

On previous projects where we have chronicled lap times with major mod levels along the way, we upgraded the tires and sometimes even the wheels right after the baseline stock laps. Sometimes we would add an an "interim" set of wheels and tires that are better than the stock rubber, but not quite the competition set we would end up with. Tires is the biggest early upgrade we can do to any project - as nothing is more important than tires to lap time performance. With the staggered wheel widths it was necessary to upgrade both wheel widths and tire widths. We had an "extreme fitment" set of 3-piece wheels already on order but I needed something to arrive in the next few days, as we wanted to get back out there and improve on the dismal baseline lap time ASAP!



Unfortunately we didn't have a significant amount of experience creating wheel fitments for the narrow body C6 (we have lots of wheel experience and sales on the C4, C5, widebody C6, and C7). With a 5-6 week wait on our "real" wheels I just wanted to get something "square" - the same widths front and back - and quickly. TireRack is notoriously hard to look for non-stock wheel sizes, but we found two options that looked like they might fit - shown above. The 18x11" OZ was a bit pricey and was a "rear only" C6 fitment that might poke on the front. Instead of taking the chance on a $1400 set of 18x11s that might not fit I went went for the Flow One F4 wheel in 19x10" - also a rear only fitment - for $400 total. I ordered these minutes after returning to the shop after Track Test #1!



Tire choice was a bit tricky as the "pandemic surge" of parts orders and shipment issues have made for a serious shortage of tire options. This reduced our choices in tires to fit these 19x10" wheels, greatly. Luckily the 275/35R19 size is not super popular in the 200 treadwear tire wars that track folks are fighting, and we got this long lasting Hankook RS-4 in that size - which I have driven on before and really liked. This compound is popular for endurance series events, as it is and not as soft (nor as fast) as the "one lap wonder" 200TW tires - A052, RE-71R, RT-660, Rival S 1.5 and the like.

The RS-4 wears VERY well on track and this tire should allow us to still get fast laps deep into a session, without having to nurse the tires and shoot for a fast lap quickly before they overheat (like the softer 200TW options - which I treat like a Hoosier A7). There was some concern that the staggered OEM tire heights front to rear might be an issue (the old front tire and new one side by side show this), but it turned out not to be the case.



There's always a fine line between light wheels and strength, but this flow formed 19x10" wheels weighed about what we expected them to - 21.8 pounds (pretty close to the 21.6 TireRack claims). Sure, an 18" wheel would be lighter and more than tall enough for the base JL9 brakes or just about ANY brakes we might use on this car. But wheel COST and quick AVAILABILITY were key here. These 19x10" wheels were on closeout at $124 retail (minus our shop discount), so it was a very cheap upgrade.



Surprisingly the stock rear 19x10" wheel and 275 tire was only 1.2 pounds heavier - we normally see a bigger drop over OEM wheels than this when going to aftermarket flow formed wheels. We had TireRack mount and balance the set, but they didn't have the TPMS sensors in stock, so we just had them use normal tire valves. We wanted this set here in a few days, and they made it happen - with one small mistake.



The math from our previous wheel measuring session (covered in my last post) showed this 19x10" would fit within the envelope Jason had designed on the front, but we still held our breath as they went on. They cleared at full steering lock in both directions and had #NoPoke at both ends. Surprisingly the stock rubber front control arm bushings are so sloppy that when backing up (reverse) at full lock the tires DO rub, ever so slightly. We will address those bushings and their gross deflection in a future round of mods.

TRACK PAD UPGRADE

So this is going on a bit of a tangent, but for a purpose. If you have ever ridden with me in an autocross or on track, one thing might jump out at you - I push the tires hard, trying to keep them loaded on the edge of their Friction Circle at all times. As such I tend to brake LATE and HARD, then get the turning phase of the turn going, and start adding throttle as soon as possible (at or before the corner's apex). I never EVER coast - I'm on the gas or brakes at some point at all times, and I always Left Foot Brake if there is no downshift needed for a corner. To me, coasting is the greatest sin when driving on track. When I am right seat coaching someone trying to find lap time, this is where we tend to find the biggest gains - by reducing any time spent coasting. This might not be how you drive, but it is how I do it, and it has worked for me.



I also transition from gas to brake after a straightaway very quickly (sometimes even abruptly) when entering a corner, then transition to trail braking, then get off the brakes as soon as possible and start feeding throttle. To some, that means I "abuse the brakes". And yes, to those that like to tip-toe and gently squeeze pedals, it seems abrupt - but my driving style (and the way I was taught) was to always keep the tire loaded. "Smooth is Fast" might be your motto, but "Coasting Is Death" is mine. When driving the same car with others and comparing data, I often extract more braking g forces, and sometimes touch the ABS limit on many cars. Nobody can say I am coasting or under-utilizing the brakes.

Could I drive faster? Sure, I'm not naive - there's always someone that can eek out more time. But after three decades of Time Trial competition, with thousands of laps data logged and analyzed, I've found that pushing the braking as late as possible is some worth lap time, for me, rather than just lifting / coasting or "easing into" the brakes. A good ABS system can cover up any abruptness on the middle pedal, and the tenths gained in braking zones can add up. I have passed a lot of lighter cars under braking after high speed straights, like into T1 or T12 at COTA.



This long tangent was written because - some people don't "understand" the brake system problems that we have uncovered when I push a car 10/10ths on track. Comments like "These Hawk HP+ brake pads work fine for me!" online are always followed by my question of "yea.... but what are your lap times?" Because driving slowly won't tax the brake system like driving faster will. My point in all of these back-and-forth comments is that NOT EVERYONE USES THE FULL CAPACITY OF THE BRAKES ON THEIR CAR when driving on track. So my driving style tends to use all of the brakes, and can quickly find weaknesses.



We looked at the C6's brakes before Track Test #1 and they looked fine. Rando parts store pads but at full depth, and the PFC twin piston front calipers looked fine, just needed a flush. After 12 hot laps at MSR in Test #1 (which is a track not known to be hard on brakes) the pads were shot and the front caliper's dust boots had caught fire and mostly burned away (hence the smoke). This isn't alarming or unexpected - I've used to PFC calipers on cars going back to the 1990s, and these dust seals are not what seals the pistons from the fluid. Real race calipers don't even have dust seals.



While the stopping power of the parts store pads was hilariously bad (as expected), we had planned on getting proper G-LOC track pads after the first test event. I wanted to drive the car first on the stock pads to see what race compounds we needed. Danny at G-LOC rushed built and shipped us a set of R12 fronts and R10 rears. As you can see above, the previously new front pads were 2/3rds worn out in just 12 hot laps. I was pressing the pedal will all of my strength on some stops - but they just don't have the friction capability when hot like real track pads do.



We staggered the pads one step in compound front to rear - using a harder R12 up front to the slightly less aggressive R10 on the rears. This is a normal technique we do for all manner of cars, based on how weight transfer naturally forces more braking abuse to front brakes versus rears. Now I normally run even more aggressive R16 front and R12 rears (which is also one step front-to-back) on most cars, but I was worried that the more aggressive R16 might be too much for the notoriously finicky Antilock Brake System programming we have noted on dozens of other GM cars. Turns out even these milder pad selections were still too much for that GM ABS...

TRACK TEST #2 APRIL 18, 2021

This was our first track test after our first real "performance modifications" to this base model C6 - the stickier tires on wider wheels plus the track worthy brake pads. We had wanted to get a performance alignment before this test but the timing didn't work out. This time Amy and I went out on a Sunday, which was also a member day at MSR on the 1.7 CCW course. The weather was perfect and we had a lot of fun that day getting our laps in.

Event Gallery: https://vorshlag.smugmug.com/Racing-...Test-2-041821/

We towed the car in the trailer again - we almost drove it out, but we managed to load the car in under 15 minutes and the truck & trailer is good peace of mind. I drag a lot of tools and electronics out to these events and didn't want to leave something behind by driving the car out. Turns out I left the Canon DSLR camera, so we got no "on track" pics other than cell phone shots.

continued below

[Fair!]

Project Update for May 4, 2021: It has been about a month since this project began and we have already completed the first two track tests and done one round of mods, with a load of parts ordered for rounds 2 and 3 to follow.



The C6 was pretty slow on track in bone stock form, and we weren't back at the shop five minutes from that event before we ordered the brake pads and three sets of wheels! One set of wheels was a mistake, but all of these sets do now have a purpose. Let's dive into the work we've done in the past 4 weeks.

REPAIR & MAINTENANCE WORK

Any 16 year old car - even one with low miles like this one - is going to need to need some maintenance over the years. The last owner deferred a few things, which is fine - we inspected the car thoroughly at the shop before we bought it, and knew all of that. It wasn't much and we chased down a few parts to get this C6 whipped back into shape.

FIX THE SQUEAK + ENGINE BAY DETAIL



There was a squeaking pulley bearing under the hood, so we bought what we thought was the likely culprit - the main serpentine belt tensioner. The hood struts were blown so those were ordered and quickly installed. I also ordered some new NGK spark plugs, Taylor 409 series plug wires, and an oil pan gasket - but we haven't installed these last 3 bits yet. You might see my new jean shorts (jorts) in the pile of parts (above right) - its called fashion!



Brad replaced the tensioner replacement and hood struts, then I detailed the engine bay after hours. It was just dirty, nothing too nasty in there, and soap and water plus some brushes and water got it all clean - then I got it all shined up with my underhood detail tricks. I have left the LS2 "coil covers" on the engine for now, just to show how stock it still is. The coolant reservoir is a little dingy so I ordered one of those new, which we will install with the full round of radiator upgrades.

OIL & FILTER + BRAKE FLUID FLUSH

Driving on track with a purpose means you are pushing the engine beyond the loads seen in a normal daily commute. And this base model has no oil cooler, which might prove to be an issue long term. As such, we didn't skimp on the new oil - Motul 5W50 Ester based synthetic does the trick.



This particular mix from Motul only comes in this weight, but for the hot and cold weather we see in Texas it works well - and I have used this exact oil on multiple cars and engine platforms. As for the filter, the Wix XP will do just fine.



This base model C6 doesn't even have much of a power steering cooler - just the "loop cooler" shown above - so we will wrap the power steering cap with a rag and zip tie to catch any fluid that might get by the cap when it first goes on track. We do this on all hydraulic power steering systems, especially on GM cars (which tend to suffer from fluid spillover at track speeds). Turns out that was a good idea, as this was the one fluid that did spew out at both track events (see top right pic) - that was a freshly detailed engine bay so all of the "shiny sports" were power steering fluid. We will flush and add synthetic fluids here and might be adding a real power steering cooler as well.



The brakes... this was a dilemma. Do we preemptively change to proper track pads or complete the first track test on these "street" pads? Jason said he had installed "the cheapest parts store pads" recently, and they were at full pad depth when we checked. I wanted to get the car on track ASAP for the baseline stock laps, so we left the stock rotors and pads in place and Brad just flushed the (black!) brake fluid for Motul RBF600 (these pads were horrible - this was a mistake).

REMOVE FRONT LICENSE PLATE

This is not something meaningful to maintenance or performance, just a styling thing that is is a personal pet peeve of mine. Removing the front license plate is a technical violation of state law here. But this is just a "paperwork violation", and no harm comes to any human being in any way by not running a front plate. Only 31 of the 50 US states require this, so it is not even a consistent law across this country. When I get pulled over for this I will tell the cop I identify as a Louisiana resident! (where it is not required).



After removing the front plate I assumed there would be two ugly holes in the painted front bumper cover, like there is on most cars fitted with a factory front license plate bracket...



I was glad to be wrong! There is just some "sticky goo" that was holding the vertical portion in place, and even after 16 years of use it was able to be removed and there wasn't a single scratch on the paint! Way to go GM - one pleasant surprise about this factory front plate bracket. I am an outlaw now, woo! Stay tuned for my 31 state crime spree and impending jail time.

SEAT TESTING & INTERIOR DETAIL

At first glance you might look at this car and think, "Sure, those look like sporty, supportive seats." Let me assure you, they are not. This is one of the least supportive seats in any modern sports car I've ever driven on track. The C7 had optional Competition seats that are crazy good, as does the C8, but the C6 generation on back had pretty much "good enough for grandpa" grand touring seats that should be replaced on any seriously tracked Corvette.



That was the biggest difference when I drove these two cars below - the C6 Z06 had the slightly more sporty versions of the base C6 seats above, whereas the C7 Grand Sport had the amazing, optional C7 Competition seats.



With both cars on the exact same tires (285/335 Michelin PSS), both driven the same day, and by the same driver (me) - the C7 GS was a full second quicker. And honestly, part of that was the seats.



It was MUCH easier to drive hard around corners in the optional Competition Sport Seats in the C7 GS. Those seats held me in so much better compared to the C6Z seats, which felt like I was gonna fly outta the damn window. REALLY have to exert a lot of upper body strength and concentration into "holding your body in place" in sub-par seats. The C6 has no such option like the C7 and C8 models do.



If you have followed any of my Forum Build Threads over the last 20 years, one of my common themes is - I always put fixed back racing seats (and usually at least a 4-point roll bar and harnesses) in every car that I track and/or autocross seriously. Even budget builds, like our GRM $2010 Challenge winning E30 (above right). Part of this is the safety aspect, sure, but mostly it is done as a driver comfort and control upgrade. Having done seat installs for 100+ customers over the last 16 years at Vorshlag, the universal response after the first time they get used on track is, "Wow! I wish I would have done this seat upgrade sooner!" It is a huge change, and is worth actual lap time. Not to mention a way to fend off back & muscle ache after a long session on track.



Here are two different stock C6 seats we weighed. The power driver's seat from our 2006 is remarkably light at 45.6 pounds (we have weighed many in the 70-80 pound range). It also has power fore-aft and height adjustment, not to mention the tilting backs like all OEM seats. We then weighed a manual adjust seat from the passenger side of my 2007 C6 Z06 (that chassis is in storage) at 40.1 pounds. Also very light, and you can barely see the deeper side bolsters on these seats - which is still not NEARLY enough support. Plus these have no shoulder harness pass-thrus or a anti-sub strap pass-thru, for use with 5/6/7 point harnesses.



We had Koenig's C5 in the shop altering his Sparco EVO II US seat placement with our prototype C5/C6 seat bracket bases, so we pulled the driver's side out, weighed it and put it into the C6. At 41.0 pounds (with our seat base, side brackets, lap and anti-sub belts, and Sparco EVO II US seat) it would work, but the "step-over" of the lower leg bolsters on these seats is pretty high, and of course there is no seat back tilt function. It was still a bit tall for me at the layback angle for the seat we needed for Koenig to fit his C5 well, and this limitation would definitely affect the seating position needed between Amy's (5'6") driving position and mine (6'3") in the C6. Fixed back seats are also a pain to use every day in a real street car, and often make it hard (or impossible) to use the OEM 3-point retracting seat belts, depending on the seat's lower design aspects.



After having driven stock C6 seats on track I knew how bad they were, so before we even took the car on track we started to look at some better Tilt Back seats, including several aftermarket versions we had on hand. The first one tested was this Sparco R333 "tuner" tilt back seat, above right. This one fits Amy's torso length well but not mine - it puts the shoulder pass-thrus several inches below the tops of my shoulders, which would compress my spine in a crash with real 6-point shoulder harnesses. That seat choice was right out.



Next we tried this Corbeau RBR tilt back seat we used to keep in our lobby. We have an older (2015) version of this seat on hand but the basic dimensions haven't changed. The side bolsters for the base (legs) and back (torso) are MUCH deeper than any OEM C6 seat. This is a steel framed / bottom mount seat (like OEMs) that comes in around 25.6 pounds. We put this old, dusty seat in the C6 to test how it fit me and Amy both.



Having driven with this RBR seat on track I know it works well for that use, even with just a 3-point belt - but it works even better with real harnesses. This one fit in the C6 very well, and as you can see (above right) the shoulder harness slots are above my shoulders, so it will work safely for taller torso heights. Amy noted that they are a little harder to get into/out of with the deep bolsters on the base. But they ARE setup for 5/6/7 point harnesses so it us still a solid choice for a dual purpose street/track car. The one down side - you cannot lean the seat forward past vertical, due to the side bolsters from the seat back and base running into each other - so if you need to get into a back seat, you really can't with these seats.



After she asked for another seat option I looked up and found this newer Corbeau RRS seat, shown above. This is essentially the same seat as the RBR on the torso section (the updated should harness pass-thrus look remarkably like the C7 sport seats now, and the current RBR has the same update) but with a more OEM like lower base section. The lower won't hold your legs in as well on its own, but will still allow a 5/6/7 point racing harness to be used, which can really holds your body in place when driving on track. It was a compromise seat that will be more friendly to street use (easier ingress/egress), so after Amy picked the material / style she liked and added the optional seat heater on the driver's seat, we ordered the pair. When you are old and/or have back problems, these seat heaters are a real life saver, trust me!



Whenever we have seats out of any street car we vacuum the carpets, and this was a good time to shampoo them as well. Tons of stuff was found underneath both, and the passenger side carpet had coffee spills that turned the hot water in our carpet shampooin'g vacuum brown. After a few passes with the hot water spray and vacuum, the carpets were clean and it smells like new inside now. We left the car open with a fan blowing on it all night to dry and then Brad put the stock seats back in. The Corbeau RRS seats shown above had a 4-5 week lead time (they just shipped, so almost exactly on time). Will show that install next time, along with a new seat base we will make for these bottom mount seats.

FANCY FLOOR MATS

This was a barely needed maintenance / interior upgrade, and might seem a silly thing to even list in this "build". It was just that the $9 parts store floor mats that came in this car were SAD. I found these "officially licensed by GM" mats online for a decent price and took a gamble...



These Lloyd's Mats are actually very well made, and these were a perfect fit for our C6. I've since found out you can custom order from their website in a number of different colors, 4 carpet thicknesses, with tons of options and embroidery patterns to choose from.



The black of these mats matches better than the pictures above would seem - it was a photo exposure thing - but I'm very happy with the result. Of course we remove the driver's side floor mat before it is driven on track, even with the OEM "hook mounts" engaged. Don't need a mat slipping under a gas pedal or something like that on track.

continued below

[Fair!]

continued from above

WHEEL MEASUREMENT SESSION

Wheels on this BASE model C6 are pretty narrow: 18x8.5" ET55 fronts and 19x10" ET79 rears. This is what we used to jokingly call the "drag pack" wheels for Corvettes back in the day, and why when we custom ordered Amy's 2005 C6 we made sure to get the Z51 package - which has wider wheels and bigger brakes, among other tweaks. Virtually all modern (C4+) Corvettes come with narrower front wheels and tires than the rear, to ensure "safe" handling - meaning UNDERSTEER. Lawyers are why most cars handle poorly, but that is an easy fix for us!



There are numerous 18x10" wheels out there that fit this car with a "Square" setup (same width front and rear), and even some 18x10.5" has been done. But our goal here was to measure a narrow body C6 for MAX FITMENT wheels. So Jason and I measured the car, using the stock wheels to go by, and our proven techniques to see what is the theoretical maximum wheel and tire widths on both ends. Then calculated the offsets and put a wheel order together.



What wheel brand and model will we use? What widths and offsets? Stay tuned and we will show you soon, after a set of custom 3-piece wheels arrive. That's right - this will not be another "Forgestar F14" wheel set for one of our cars, as none of their one piece, flow formed wheels can be built to the offsets needed to fit this car's fender limits. This is with another wheel brand we've been quietly working with, and I want to show off their work. It will likely be the most extravagant purchase for this entire project, but WHEELS MAKE THE BUILD.



We will make some suspension tweaks to be able to fit these but we WILL NOT be adding the C6 "widebody" fenders to clear bigger tires. Why? Well, after a lively debate internally, we concluded that converting a narrow C6 to the OEM widebody fenders takes a LOT of time and money - which could be better spent on the 3 other shop owned race car builds, not to mention the many customer builds that are demanding all of the hours we can throw at them to be completed.



And yes, the widebody C6 is my favorite car GM has ever built, so this was not an easy decision to stay narrow body. The wider C6 cars - Z06. Grand Sport, ZR1 - can fit SO much tire under the stock fenders! (see above) But again, our narrow C6 build will be pretty limited on scope and quick to complete, minimizing shop hours and costs. The narrow body C6 is also extremely undervalued and under appreciated in the (still flaming hot) used car market - we aim to see how far we can push one of these, on a budget.

C6 BRAKE OPTIONS AND UPGRADE PATH?

I learned a good bit from some recent research, including from this Corvette Forum post. The base C6 non Z51 has the JL9 brakes. The J55 brakes are on the Z51 and later model year F55 option C6. The J56 brakes are the option on both the Z06 and Grand Sport models.J57 is the carbon ceramic brake package on the ZR1 and Z07 Z06 models.

• JL9 - Front 325mm/12.8"; Rear 305mm/12" (base model)
• J55 - Front 340mm/13.4"; Rear 330mm/13" (Z51 model)
• J56 - Front 355mm/14"; Rear 340mm/13.4" (Z06 and GS)
• J57 - Front 394mm/15.5"; Rear 380mm/15" (ZR1 and Z06/Z07)

Apparently the front calipers are exactly the same for both the JL9 and J55. The rear calipers of the J55/Z51 have slightly smaller pistons than a rear JL9 caliper in order to maintain the correct front/rear hydraulic bias with the larger rotors of the Z51. Most likely we will convert our base JL9 brakes to the larger Z51 brakes, which is very cost effective.



All model C6 Corvettes have factory front and rear brake ducting, and I will show more of this in future updates. Amy's JL9 rear brakes (above left) are incredibly small and instead of spending hundreds of dollars on track brake pads for these we will upgrade the rotors and calipers to the similar but larger J55 from the Z51. I will show costs for each mod done to this car and the J55 brake upgrade and refresh will be one of the most affordable upgrades. Going to the J56 brakes (above right) would cost more than 5x as much.

RELIABILITY MODS

We want to be able to drive this car to local events. Nothing sucks worse than driving to the track and having something break, with no truck/trailer to bring you home. To proactively prevent some of this drama we will do a number of upgrades to make this car ultra reliable and bulletproof. Two of the things that come to mind are cooling and oil control. With the higher temps we see in Texas and the higher grip we will see with "tires that start with a 3" we are pushing the stock cooling and oil pan beyond their capabilities.

The factory C6 radiator is a tiny little thing with plastic end tanks, and at 16 years old things are probably starting to get brittle. I know we will tax the limits of the stock cooling system in the Texas summer months, even with a bone stock 6.0L LS2 engine. We will replace the radiator soon with something like this massive DeWitt Pro Series aluminum radiator (below left). They make drop-in replacements that massively improve cooling capacity and efficiency. That is the unit Koenig's C5 has now and it is ROCK SOLID reliable. We recently ran his car at an "autocross" that was actually held on a road course, and with two drivers making 10+ runs back to back, never shutting off for nearly 90 minutes... it sat at 205°F all day (the thermostat opening).



The other big thing we HAVE to do soon is an Improved Racing oil pan baffle / crank scraper, shown above. Any LS engine has pretty poor oil drain back onto the spinning crank, which turns the oil to foam and burns it under hard use. High G lateral and braking can also slosh oil away from the pump's pickup.

This car has a "wet sump" LS2 engine - but these can and do last on track IF you keep the oil pick-up submerged in liquid oil at all times (a dry sump isn't "required" for track use, like some people like to insist). A better oil pan baffle is usually all you need, and of course, keeping an eye on the oil level after every track session. The oil pan gasket seems to be leaking on this car right now, so dropping the pan to fix that was already on the list. Adding the baffle isn't much more work when you have the oil pan off.



We also want to keep an eye on the oil temps. Going to an external oil cooler (like this Derale 10000 series below left, on a customer's endurance CTS-V) would give me a good excuse to replace the "thimble sized" oil filter that all LS engines are stuck with (above right). If we do an oil cooler we will also add an external oil filter with a thermostatic bypass (below right, Improved Racing unit we like to put on lots of cars). That let's us move to a MUCH larger and more effective oil filter.



We won't jump off into that set of modifications unless the oil temps noted during track driving push us over safe levels (275-300°F max temp is about the limit I go by for reliable oil system use).

WHAT'S NEXT?

I have started cleaning things and ordering parts, and of course our new fashion needs. That is enough for an intro post.



We will setup a time at a local shop to get a baseline wheel dyno test, then at MSR-C to get the baseline laps in on these stock 245/275 all seasons. Then we will write another post after the video and dyno charts plus the initial suspension bits, wheels and tires, and other changes in store.

Thanks for reading,

[Fair!]

Re: Vorshlag C6 Corvette Development + Shop C6 Z06 Race Car (Rampage)

continued from above

These are the M8 nutserts - threaded inserts that install like a blind rivet - which we used to install the inner fender structures in some hidden locations. As you can see below, the factory used these in the same size in the bottom of the frame rails.



The ends of these boxed, hydro-formed frame rails are usually capped off and inaccessible on the inside, so bolts & nuts are not an option down in here.



On the exposed upper flanges of the frame rail (see above left) we used thru-bolts with nuts on the back side. With the additional holes drilled into the frame and inner structure bolted down the inner and fender were shimmed and fitted, so that the fender lined up with the door. We can unbolt this fender and the inner structure now in about 15 minutes for "deep access" to the engine bay, at least on this right side.



Once that right side fender was installed, the left front went on and lined up somewhat easily. Now it was time for the hood - which we got with the chassis purchase, from a red C6 - but first, we had to source stock hood hinges and repair the studs those bolt to at the frame.



These new OEM hinges above were able to bolt up to the two studs sitting on top of the frame rails after some minor repair. Whoever chopped the ends of the rails off left just enough meat in there to keep the studs, and one bent one was later reinforced and welded (see the "capped end" work below).



With the hinges loosely assembled to the frame rails, the hood was then installed. Then the hood and fenders could be adjusted to line up together and up against the front edge of both doors. We removed the factory hood latches and cable release at the firewall (heavy) and will instead use a pair of AeroCatch latches when we pick the final hood (won't be this red one).



Next up Ryan made a small aluminum support panel for the underside of the tear in the Grand Sport widebody front nose. This bumper cover included some of the OEM structural bits, so it was easier to line up the tear than a bare bumper cover itself. He bonded the small support panel to the underside of the flexible cover with epoxy and let it set up overnight.



The front section of the frame rails had been hacked off to repair another car - so instead of robbing another chassis of these ends ($$$) and painfully lining those up, I decided to just make a crash bar from aluminum tubing. I asked Ryan to clean up the cut-off ends of the aluminum frame rails, to square them up and make the ends symmetrical, side to side. He then made some flat plate sections to cap off the rails and TIG welded those to the cut frame ends. We will come back and bolt a tubular aluminum front crash bar to these sections later.



We sourced the crash bar tubing in 6061-T6 aluminum (above left) but we were tight on time (my shop cars pay the company $0/hour!) and Ryan had already lined up the nose structure to a bunch of additional brackets we sourced from GM (above right). So he was able to line up the front nose to the chassis without the crash beam in place (which we will definitely add later).



Next up a pair of used C6 headlights I sourced from eBay were installed. I looked for new units but they are 4 figures each - no cost effective knock-offs exist yet. These OEM units were $400 for the pair, which is unusually cheap for a complete set of even used C6 lights - but unlike the pictures online, these were all full of sand (?!) and had scratched lenses when they arrived. I should have known that the "unbelievably low price" meant they looked nothing like the pictures in the ad. What can I say - "typical eBay purchase". The nose was installed finally and everything lined up together.

TEMPORARY STEERING COLUMN

The stock steering column was removed (and the steering wheel was missing) when the interior was stripped. But soon we will need to steer this car on and off a trailer, for transport while the bodywork is being made. We have an electric assist column in the plans long term but we needed something - now.



I asked our crew to build this temporary steering column, shown above. In hindsight we could have just reinstalled the OEM steering column and just bought a steering wheel and hub adapter, but I wasn't ready to pick the steering wheel just yet, and the GM hub adapter wouldn't be re-used, so instead I bought $60 worth of parts above. It looks terrible, but will be tossed out when we make a proper racing column for the car later (just an OEM to 6-bolt hub adapter is $90 + a $250 steering wheel = this was cheaper for temp use).

LOTS OF OEM LIGHTS/GRILLS/SILLY BITS

After getting the car looking mostly complete, the guys at Anderson wanted to see more of the OEM bits if they were going to make a replacement nose in carbon. So I spent a couple of months chasing down all sorts of grill inserts, fog lights, turn signal / side lights, and more.



Valuable lesson learned here. So I did find knock-off fog lights, which are apparently damaged often enough to support this line of cheaper offerings. And the base C6 vs the widebody C6 look very different, yet all of the online offerings show the same part number. The parts above arrived and they look "wrong", so I paid to send them back and then bought OEM replacements from GM for 3x the cost.



Joke is on me - turns out the same foglight fits both the base and widebody C6 noses, even though the foglight openings are wildly different in shape. The larger "base" foglight shape is covered up by the widebody nose's opening. There is a carrier on the inside of the bumper cover the matches up perfectly to the weirdly shaped foglight. I never even thought to check the cheaper ones I bought online. Oh well, now I know. And no, these will likely never be used on our car in racing trim - just got these bits for Anderson to verify molds if they make the carbon nose replacement.



These side marker lights mount to the nose and I found knock-offs for the OEM parts, which I ordered. Annnnd that order was cancelled, due to lack of stock. So I sourced these from GM for 2x the cost. Another piece likely never to see racing use, just need for Anderson's checks if they make the nose.



Brad and I both spent some time with the heat gun, solvents and an eraser wheel on a drill removing some dried adhesive that was baked onto the paint. This was from clear adhesive backed film that was used to cover the open windows (which were there but the battery had been removed) and gaping maw of the missing windshield. This caked on stuff was a real pain to remove, but the eraser wheel worked the best - after the car was left outside in the sun to soften the dried adhesive. Cleaned up and ready to transport to California in late March!



We fought for two months with transport companies and in late May we finally found one that would 1) transport a non-running car, 2) would transport a car without a windshield (enclosed transports only), and 3) that actually showed up! Now the truck that arrived was an enclosed ramp truck had no winch, so it took 8 people to push it up the steep ramp into the truck. At least it steered and the e-brake worked. Anderson has the car now and should hopefully have it wrapped up and ready to transport back to us in July or August?

TERMS OF RAMPAGEMENT

It was a lot of months chasing down parts and re-assembling this car, but it was finally shipped out just before we moved our shop. But this car needed a name before it left...

Those of you who are not fans of the hit animated series ARCHER might be wondering why the hell are we calling this car "Rampage"?? First, go back and read the build thread for our C4 Corvette, Project Dangerzone. Notice the Archer themed jokes? If you don't watch Archer you are missing out on a lot of one liners.



In Archer season 2 episode 9 called "Placebo Effect", Archer gets cancer. When he discovers the chemotherapy drugs he's been taking for his breast cancer are counterfeit (sugar pills and Zima), he sets out to destroy the Irish Mob criminals behind the scheme. He goes on a "Rampage", killing everyone involved with the fake chemo drug ring... so pretty much how driving this Corvette will be like, right?



Expect to see ZIMA sponsorships (a tasty 1990s malt beverage), breast cancer awareness decals (legit), some taunts to the Irish, of course a few other Archer series nods on this car when it hits the track.



We transferred the "RAMPAGE" rear plate from the DangerZone C4 over to the C6Z. Along with adding a new the C6 OEM bumper cover (shown above) and some structural bits needed to mount it - all of which I bought from GM. Hoping that Anderson will also turn this rear cover into a carbon piece, but I doubt it. I'll be happy with all 4 fenders and both doors being carbon - anything else is a bonus. These parts are slated for production so everyone can buy them, once they are ready.

WHAT'S NEXT?

We are busy working on a number of other shop projects and lots of customer builds, of course. The shop move is done but construction continues, so I am kind of glad the C6 is at Anderson for another month or so.



Since starting on this C6Z we have painted, finished and sold my BMW E46 330 "daily driven track car" experiment (above left), so we were left with nothing to race. So in late February 2018 we bought this red 2018 Mustang GT (above right) and have already done two rounds of mods, lots of track testing, raced it in NASA and SCCA Time Trial events as well as an Optima series event. There are build threads for both of these on the Vorshlag forum, linked in this paragraph.



Meanwhile HorsePower-Research has been building these tall deck aluminum block 527" LS7 engines in ever crazier versions. Its the biggest LS engine in the world, at 8.6 liters! The 1/2" taller deck height on the RHS aluminum block is hard to even see unless you know what to look for. So we are thinking about using one of these for our C6 here. You can read more about some of the street car versions of this 527 that made 720 whp on E85 at this link. With some more advanced heads, a custom intake manifold, more compression (race fuel) and a conservative 8000 rpm power peak, it could sneak up on "four digit power". So... pretty much a Rampage.

More soon,

[Fair!]

Re: Vorshlag C6 Corvette Development + Shop C6 Z06 Race Car (Rampage)

Project Update for July 9th, 2018: It has been a while since I first posted about this C6Z shop build but we have been moving forward with this chassis. I'm buried in new shop construction but will take a moment to try to catch up on Project Rampage.

THE SEARCH FOR CARBON BODYWORK

A lot of what I share in our build threads is done to help you, our readers, from avoiding the mistakes I have made in the past 34 years of wrenching on cars. Often I need to re-learn the same lessons I have learned before. This was one of those times. Being Cheap is rarely the right call.



Remember - I bought this 2007 C6 as rolling chassis and it was missing a lot of parts: the engine, both front carbon fiber Z06 fenders, one of the front inner fender composite structures, the hood, and the rear fenders were off the car - among other things. The OEM front fenders on the C6 Z06 are the only real carbon fiber parts on the C6 Z06 (the ZR1 has these + a carbon targa roof panel). The rest of the car is straight up "fiberglass" composite, but the C6 versions of the Z06/ZR1/GS also have an aluminum hydroformed frame - a first for GM.


Not many OEM cars can fit a 335mm front or 345mm rear tire with properly sized wheels!

There are two distinct sets of bodywork for the C6 chassis: the base/convertible "narrow body" and the Z06, Grand Sport, and ZR1 "wide body". The differences in the wide body front and rear fenders (and front under structures) allow us to fit MUCH wider tires on these C6 models vs the the narrow body C6. Like these monster 18x12" front and 18x13" rear wheels are on our tester Jerry's C6 Z06 shown above. This car has stock fenders and swallows 335mm front and 345mm rear Hoosiers. We have sold lots of wheels for C6 widebodies in this size.


These are the fender mods needed for an E46 M3 to fit the 335F/345R tires!

We are able to fit these with no body work whatsoever. Do you realize how hard this wheel/tire setup is to fit to other cars???? The E46 M3 above has 62 hours of custom metal work to clear these same wheel/tire sizes.

OEM C6Z WIDEBODY FENDERS?

I went looking for C6 widebody OEM fenders the WEEK after I brought this car to Vorshlag in August 2017. What were the parameters of the fenders I sought out? Well first was strength. The OEM ZR1/Z06/GS "wide body" fenders are very light but also very fragile - racers and mechanics complain of how easy it is to crack these just leaning on them doing underhood work. And the way I drive they might take a few "off track" excursions. So I wanted something stronger than the fly weight stock front fenders.


The only real "carbon" on the C6 widebody are the front fenders. VERY light... maybe too light?

Next up was cost. Wow, the OEM carbon wide body fenders are PRICEY! They can cost $2000/each new and even $800-1000/each used (+ shipping), and most of the used stuff is damaged even at those prices. So I looked at aftermarket stuff....

FENDERS WIDER THAN OEM C6Z WIDEBODY?



These "super wide" front fenders by Supervettes seemed pretty slick. These come in all 3 C6 widebody variants: the Z06, the ZR1 and the Grand Sport, and each of these had unique fender vents. After talking to their composites guy he said most people buy the ZR1 version, the Z06 is rarely chosen and only one guy has ever bought the GS style. I had considered buying their extra-wide Z06 front fenders at $1900 in fiberglass or carbon at $2300, but just couldn't make myself do it.



I had seen these in person - these fiberglass ZR1 style Supervettes fenders on the C6 Z06 above belong to the owner at the body shop where I bought my rolling chassis - but the rears looked almost ridiculously wide. Maybe I was just being too picky and cheap? The fit was good but they do take some work to fit to the chassis, and they are a bit heavier. And since tires wider than 345mm rears don't really exist, what is the point? This option seemed more "stancey" than "racey".

LOW COST ZR1 CLONE FENDERS?



Next up I looked one of our vendors who makes composite fenders, hoods, and complete body kits. This company has multiple names: Extreme Dimensions, Carbon Creations, and Duraflex are the main three we have dealt with. We used their Duraflex (flexible fiberglass) nose on the widebody E46 M3, shown earlier.



They make "ZR1" style front fenders (above left) had a hybrid C7 / C6 front nose (above right) that looked like it might be cleaner aerodynamically than the Z06/GS/ZR1 nose (their OEM front noses are identical and are made for the widebody C6 OEM front fenders). Their website was unclear if this C7 "stingray" nose fit the wide or narrow front fenders.



After months of deliberations and searching for used OEM wide body C6 fenders to no avail, I broke down and bought their "carbon" front "ZR1 style" fenders and this C7 look "Stingray" nose. Again, their website was vague as to which C6 models these would fit - they claimed wider than stock and that they fit "all C6 models", but was that wider than C6 narrow body or wider than C6 GS/Z06/ZR1 widebody? I had several emails and calls with them before purchasing these fenders, the nose and a matching lower splitter section (to make the bottom flat so we could build a real splitter from there) shipped by freight truck to our shop.



I am the first one to tell you that some import composite parts will not always work like they claim, but I needed to re-learn this lesson again. These front fenders simply do not fit an OEM widebody C6 chassis. Turns out they were made for the base model "narrow body" C6 chassis/nose and just look like ZR1 fenders. We would have had to cut giant chunks of the wider inner structure off to make these narrow body / narrower fenders "fit" our widebody C6 chassis. No thanks.



And even if we had done this modification, these were nearly double the weight of the OEM carbon fenders and - more importantly - at least 2" narrower than real ZR1/Z06/GS fenders, per side. Luckily my emails up front to them made it very clear up front that we needed as wide or wider than ZR1/Z06 fenders, so they allowed me to return all of their bodywork for a refund, minus shipping both ways (about $330). I figured the $330 was the cost of learning this lesson. They said they would update their catalog, to remove any confusion for others in the future. As of this writing I still have not found a cheap widebody C6 ZR1/Z06 front fender.


This Duraflex 6 piece flare kit for the 86 chassis is about $400 and easily covers an 11" wide wheel

Now I don't want to disparage this company (Extreme Dimensions / Carbon Creations / Duraflex) because their products to have a place in racing / car builds, and they have a MASSIVE catalog. Like I showed earlier, we used their 1M nose on an E46 M3, and I have recently purchased the Duraflex 86/FR-S/BRZ flare shown above for use on our shop 2013 FR-S. These bolt-on flares should easily cover the 18x11" wheels we have coming for this car, which should work well with 315mm tires and V8 power.

BACK TO FINDING OEM C6 WIDEBODY FRONT FENDERS?



After nearly 6 more months of searches, I came upon these used black OEM C6 ZR1 front fenders, shown above. They looked nearly perfect and the price was right (still cost 4 figures).



I also managed to score a free nose from a C6 Grand Sport - which needed some repairs but was easily fixed - from my painter friend Shiloh. With as tight as my budget was at the beginning of 2018 (in the middle of building a new shop, upcoming move, expanding our CNC machines), this was exactly what I needed.

LET'S SEE IF WE CAN HAVE SOME CARBON ZR1 WIDEBODY FENDERS MADE!

I was still worried about damaging these fragile, expensive OEM carbon front fenders on track, so I made a deal at the 2017 PRI show to send our C6Z chassis - with OEM bodywork attached - to a manufacturer who makes real carbon fiber parts, at affordable prices.



The deal was they would use our car to make molds for replacement front fenders, rear fenders, and doors (maybe some other bits) in carbon fiber, made for racing use - similar weights as the OEM rear fenders, lighter than stock doors, and as close in weight as the carbon fronts - plus stronger and more cost effective. This way, if I stuff the car into a tire wall I'm not out one hojillion dollars for new OEM bodywork!



Now i needed to get all of the OEM bits ordered and installed onto our rolling chassis, then arrange for transport to the west coast...

ORDERING OEM PARTS + ASSEMBLY

As I started in a previous post, I bought this 2007 Z06 chassis as a rolling chassis, partially disassembled. The body shop I bought it from took a complete car and started picking parts off to use to fix wrecked C6 Z06 cars that had rebuilt / salvage titles. Our car had a "parts only" title, due to a paperwork issue with an insurance claim, so it was impossible to sell to be used for street use. For a race car, however, its perfect.



They had taken the right front inner fender structure off of this car - which is a fiberglass piece normally bonded to the frame. It is a LOT of work to remove cleanly, and even more work to reinstall with the factory thick epoxy goo for a repair to another chassis. Essentially if you damage this piece in a crash, you should buy a new one from GM, remove the old one, bond in the new one with a 24-hour set epoxy, and temporarily install the rest of the bodywork to line it up right.



Well we got another widebody C6 removed structure from this car with the purchase - why they removed it is anyone's guess. Instead of bonding it to the aluminum chassis I decided to have it bolt on, which will make it easier to perform some of the underhood fab work we have planned. The C4 Corvette chassis (above) had a more accessible engine bay due to the large (and heavy) clam shell hood/upper fender sections, and bolting this inner section on will give us similar room on the C6 - albeit without the ease of just opening the hood.



It looks like whoever tried to remove the bonded inner fiberglass structure from this car damaged it pretty badly (see above) - there are big chunks of fiberglass still stuck to this frame. Those areas had to be sanded away before we could install the used OEM "widebody" inner structure we got onto this chassis.



Brad used a heat gun and some scrapers to loosen the epoxy goo and removed all traces of it from the aluminum frame rail. It took some patience and elbow grease, but eventually it was all removed - as well as the fiberglass fragments. With the aluminum frame rails now bare, we could attach the replacement inner.



We began by acquiring a gaggle of OEM parts to get this car put back together externally, to then ship the car to Anderson Composites in the first part of 2018 for molds. We lined up the fender liners, some front bumper cover support parts, the front bumper cover from a C6 Grand Sport, and the ZR1 fenders mentioned above.



Brad began fitting the right front inner fender support in late January - after we ordered some M8 nutsert parts and tools for some of the inaccessible parts of the frame. Some of the bolts we used to attach this inner were into "blind" areas, and some were thru-bolts, as shown above.



Bolting these inners on instead of bonding lets us shim them to fit perfectly, to get the fender gaps right.

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