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Unread 08-16-2016, 12:42 PM
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Join Date: Jul 2004
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Default Re: Vorshlag Ford Focus RS Development Thread

continued from above


Left: Enkei 18x10.5" wheel and 275/35/18 Yokohama was 48.5 pounds. Right: This big tire and wheel lowered lap times on the EVO!

The first things we did were add proper monotube coilover dampers, upped the spring rate, and lots more negative camber to the front end - which is the same order of mods we have planned for the RS. We then upgraded the wheels to wider 18x10.5" wide Enkeis with 275mm wide good street tires (Yokohama Advan AD07). Again, similar in tire width (275) and wheel width (9.5" or 10") we have planned for the RS. I don't think the RS can fit as much wheel as the EVO X, but we'll soon see after the coilovers are installed.


With monotube coilovers, more spring rate, swaybars, camber plates, and wider wheels/tires - this EVO X cornered flatter and was much faster

Like we have planned on the RS, we focused our changes on the EVO X on the same basic suspension upgrades - minimize body roll, reduce suspension bushing deflection, add negative camber, improve dampers and up the spring rates dramatically. Then we added wheel and tire width to improve mechanical grip.



This EVO X MR also had a major flaw on track - we had to quickly make some cooling upgrades the MR's transmission cooler. The Getrag DSG semi-automatic trans ran hot on track (after 10-12 minutes it would overtemp the trans and go into limp mode) until we opened up the front cooling duct and added a fan. Like the oddly placed intercooler decal covering 1/4 of the front heat exchanger on the RS, the MR had a large transmission fluid cooler that was 1/2 covered up by a foglight. We removed the fog light, meshed the now larger openings (to keep rocks/bugs/klag from packing up the heat exchanger), and then added a 5" electric cooling fan to use in the pits between sessions to cool this fluid. Cured the over-temp issue and allowed the EVO to run complete 20 minute track sessions without fail.



So looking back on it, the EVO X MR we raced for 2 years was far from perfect in stock form. With some work, a lot of testing, some upgraded components, and the help of others we were able to make it more reliable and much faster. Hopefully we can do the same with the RS. COBB did the tuning on our shop EVO X and they have already tuned Todd's Focus RS as well. Evolution Dynamics also has some tricks up their sleeve, as do other partner shops that are working on this car. It looks like we might just be able to cure what ails the RS. Stay tuned!

MICHELIN PSS SPECIFIC ADVICE AND 500 PSI

Like I said in the beginning, everyone on the internets seems to be questioning every single thing we wrote about in our first 2 posts. One of those was tire pressures we used on the stock 235/35/19 Michelin Pilot Super Sports, or MPSS for short.



This 300 treadwear Michelin tire is a great all around performance street tire, and while somewhat alignment sensitive, it tends to wear well over many thousands of street miles when used correctly. The MPSS can work well enough on track, when the suspension is optimized, but this tire is by no means the hot "street tire" for track use. We recommend this tire for daily driver use to most people that ask because it is a quality tire, has decent performance, long life, and comes in a lot of sizes.

Currently there are probably a dozen tires in the 180-200 treadwear range that are faster than the MPSS: the Bridgestone RE71R, BFGoodrich Rival-S, Dunlop Direzza Start Spec II, Hankook R-S3-V2, Yokohama AD08R, and even Michelin themselves make several models faster than the MPSS. Because of our many years competing in Optima, Goodguy, and SCCA Street Touring classes, we have to know these tires very well and stay on top of any new comers or changes in the "200 treadwear tire wars".



None of these "super fast" 200 TW tires listed above are really appropriate for true "all weather daily driver use", as determined by most OEM car makers, so Ford went with a good compromise in the MPSS. This tire is an upgrade over what Ford puts on a LOT of its hot performance cars, so we have no complaints there - other than the narrow size they chose. A 245mm width in a 17" or 18" diameter would have been a more appropriate factory tire size for this car, given its weight and power level. But those 19" wheels had the look Ford wanted, so styling won out over weight, practicality or performance.

We have used many sets of Michelin PSS tires on many cars on track, as well as dozens of other brands and models, what we have learned is - there is no magic tire pressure to run on all cars, even tires of the same model/brand. There are so many variables that affect tire pressure, it would fill a book.


Tracking with 245mm wide MPSS tires at ECR on BRZ

For example: on this lightweight (2775 pounds) rear wheel drive Subaru BRZ above was run on a 245mm MPSS for both street and track use on a 17x9" wheel (we later moved up to 255mm BFG Rival tires). After track testing we ended up with around 32 psi hot tire pressures on the MPSS. These lower pressures can work better on lighter cars and/or cars with a better tire-width-to-weight ratio. We had really good suspension (MCS 2 way coilovers) and excellent camber (Vorshlag plates) and good swaybars on this BRZ, too. It cornered flat, had plenty of static negative camber, and a well supported tire of proper width for the weight and power - so it treated the tires well. This car with this tire had a similar weight-to-tire-width ratio to most Corvettes.


Left: 215 vs 245mm tires. Right: The FR-S/BRZ's main weakness in stock form were the craptasitc, skinny tires they came fitted with

Funny thing is - we made a big deal about how TERRIBLE the factory tires were on the BRZ and FR-S. I gave that car more grief than I did the RS. Of course at the time, this was scandalous - "Why do the magazine writers rave about this car if the tires are so bad??", they said. There were fan boys of this car as well, but the fact was that the skinny 215mm "Prius" tires they fitted to the 86 twins were a joke. Over time many thousands of BRZ/FR-S owners have upgraded to better 245-255 mm tires, which we recommended from day 1.



Toyota and Subaru missed a number of things on the 86 chassis design, which I was just as vocal about in that project build thread. The ridiculously wide FA20 2.0L engine makes underwhelming amounts of power for this car. The engine is placed about a foot farther forward in the engine bay than needed, which helped contribute to the relatively poor 56% front weight bias - pretty awful for a RWD car.

Overall the 86 twins are still nice handling cars due to two important facts: they weighed in staggering 670 pound lighter than the RS, and the track width is very wide for a car this light. Granted, the RS can likely eat this BRZ's lunch on a road course in stock form, especially with the little Pruis tires the factory fitted. By the time we were done this BRZ, however, it was an autocross and track terror with zero power mods. I ran laps as fast as the 420 hp 2013 Mustang GT at ECR (2:07s) in the 200 hp BRZ.



Honestly the "86 twins" are cars that people should also look at if they want to have fun on track or autocross. Yes, even versus the Focus RS. That seems crazy - it has 150 less hp and 2 fewer drive wheels - but this comparison can be made simply because the chassis is so much lighter. It has a decent suspension setup, lower center of gravity, decent RWD Torsen differential (no robots, computers, or NASA scientists needed) and again... it is 670 pounds lighter than an RS.

OK that was quite a tangent. Back to the MPSS tires and our starting pressures... My point somewhere in this section was: We get a lot of people asking us "what tire pressure should I run?". I mean hundreds and hundreds of people ask this, all the time, everywhere. Tire pressures, as I said above, are important but they are actually fairly hard to give gross generalizations about. Too many variables. And when people ask this question, they never tell us much about their cars, tires, wheels, setup, or end use.



It is even more frustrating on social media, where the previous day's technical help we post gets flushed down the toilet, and the same questions pop up the next day. Snapchat group think - ask, answer, forget, then rinse and repeat tomorrow. At least here, on a real forum, we can point to our answers from a previous post.



This has gotten so frustrating that we have created a sarcastic reply of "500 psi" to all tire pressure questions. Why? There are just too many variables that go into optimal tire pressures that it is impossible for us to tell folks what they should use - unless we get a lot of data about their car and we happen to have tested that tire model under those circumstances. Every car's set of variables is slightly different, and only long term, scientific testing can tell someone what their optimal air pressures are: for their car, on their tire model/width, there wheel width, their suspension/settings, and their track surface, their driving style/setup, and in their common weather/track temps.

So when you see our 500psi decals, this is our way of saying there is no one right answer for tire pressures. You need to test for yourself, for your circumstances. Now you know.

WHAT'S NEXT?

Our true goal in writing these posts is to show fixes to the problems that we have seen on the RS. To make these cars faster and more reliable on track. My next post will finally have some solutions instead of just critiques and explanations.



So far this RS has logged 4400 miles and been run at 3 different road course venues on the stock suspension in the first month of ownership. The suspension will all change drastically, starting this week. Todd just dropped the RS off today for another 2 week period and we are working on our new Focus RS/ST camber plate design right now (for coilover use).



After pulling the engine undertray and front end off we have great "underskirt" pictures of the RS in new areas. Look for those in my next post.



With the front end off we are measuring for placement of a large external liquid-to-air oil cooler. We're going to try to fix that issue before the next track test and road course event. More partners have come on board with upgraded parts, after seeing this form thread and noting Todd's and our track testing. Lots of new parts will be installed in the next 2 weeks. Which is good, since Todd is running the RS at the 2 day Optima @ Road America competition Aug 27-28th. We are hopefully going to be track testing the new suspension, exhaust and oil cooler before he leaves, so we have a tight deadline.

Thanks for reading,
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