97 M3/4/5 running in STU

[97M3]

Re: 97 M3/4/5 running in STU

Ran the alignment specs given with Konis set to full stiff, tire pressure 36psi cold all the way around.

Only got out usual three runs but tires heated up to 40/41psi on all 4 corners. A couple of pics taken show alot of sidewall flex... Will increase pressure a couple of lbs this weekend.

Car pushed even with 245s all the way around. Want take a turn out of the front struts.

Any other suggestions?

[Chris]

Re: 97 M3/4/5 running in STU

I've found 34psi to be the happy spot for the Dunlops (with adequate negative camber).

Most of being competitive in this car locally is seat time. I haven't changed much over the last year and am pretty close behind the fast boost buggies locally now... Close as in, some days I can lay down faster times than our de-facto yardstick Russ (who was 5th this year at Nats).

255s are a big step up from the 245s, especially on a 9"+ wheel. The grip difference is immediate and very apparent.

To be really competitive I think you'll want stiffer springs. I'm running 570/625 and will be going stiffer most likely. I like the balance of the car now but there's still a fair amount of body motion.

I'll post more as time permits...

[97M3]

Re: 97 M3/4/5 running in STU

Thanks for all the advice. Will let you know how she does her first day out. We expect to use the severla slush events to complete shakedown beofre next years BMWCCA and SCCA events.

Once we parked Olivia next to the Z3 last week the Z3's #40 aux fan fuse blew. Going to be a tough year...

[Fair!]

Re: 97 M3/4/5 running in STU

The suspension is TCKline coilover with 450/550 springs and single adjustable Konis. The tires are 245/40-17 Star Specs.

How firm should the shock settings be?

Shock settings really depend on the entire suspension set-up, surface, conditions, temperature, your driving style, etc. One man's settings on a different car/day/course have almost ZERO relevance to yours.

This shock tuning guide is helpful to our customers, so give it a shot: http://www.vorshlag.com/documents/Tuning_AST_Shocks.pdf

What alignment should we go with THIS Sunday?

Alignments are pretty simple for an E36....

Run -3.5 to -4 degrees of negative camber in front, about -2 to -2.5 in rear. 1/2" of total toe in in the rear, maybe as much as 1/8" total toe out up front. Max positive caster in front, so long as you don't infringe on the camber settings noted above.

Someone throw out their tire pressures they run NOW.

Again, this is something you have to look at to judge, and changes depending on the surface and temps. Start at ~35 psi front, 32 psi rear and adjust up down depending on the handling characteristics and based on the scrub on the edges of the tires. If the car has a push, run more front pressure or less rear. Conversely, if its loose run more rear pressure or less front. If someone tells you otherwise they are misinformed (and yes, people get this simple aspect of tire pressure tuning ass-backwards all the time). The tire pressures will creep up after every run - check and equalize them to your base setting after every run, or alter them and note the change in your log book.

If the edges of the tire shoulder are scrubbing down the sidewall, run more air pressure on that end of the car. A $20 air pressure tank can be purchased at most auto parts stores - fill it up and take it to the grid with you. The wite shoe polish applied on the edges trick works well for newbies, but after a while you can see fresh scrubbing without getting that white stuff everywhere.

When making tire pressure changes make BIG ones at first, until you get the hang of it. I hear people claiming that "that half psi change transformed the car!". I make fun of those people, too. 2 psi changes are normal, but when finding a new set-up like you are doing, maybe even 4-5 psi jumps are needed. Its unusual to need more than 40 psi in a tire like that, unless the car is really set-up poorly or the tires don't fit the wheels well. I've used 50 psi tire pressures in a very poor handling car before, but that's probably outside of the range you'd ever need on a BMW.

With a 245mm tire on an 8.5" wheel, that's a bit squeezed, so running a tick more tire pressure than normal may help keep the tire more square on the rim. Its a trick to help compensate for a narrow wheel. A (edit) 245mm tire works OK on an 8.5" wheel, but better on a 9" wide wheel wheel.


255/40/17 on 17x9.5" wheel

There are other tricks to help you find the optimal set-up, including:



1. Timed testing at practice events. Invaluable.
2. Finding a faster and more experienced co-driver. You can't teach this sport to yourself.
3. Observing pictures of your car loaded in a corner at events. Look for positive camber on any tire that's being loaded and keep adding more negative camber (or spring rate or swaybar or etc) to eliminate that. A loaded radial tire should still have a tick negative camber, as shown in the picture above - the front looks about perfect, but the back could have used a tick more negative.
4. Pyrometer testing can help you nail down tire pressure and camber settings, but its best done at a practice event with a skidpad and a helper. You have to get measurements QUICKLY.
5. Data acquisition testing at each and every event you attend can help you amass a lot of data about your set-up and driving. Get a data logger with multiple accelerometers and a GPS sensor and log every run.
6. An autocross log book should be made for every car to catalog every run at every event you attend. Write down initial tire pressures and shock settings and fill in your observations and changes after every run.

Cheers,

[Redwood]

Re: 97 M3/4/5 running in STU

I have TC Kline Koni SAs on my E46 and I run full stiff up front and about half a turn on the rears. Your mileage may vary, etc. Thanks for the tire pressures, Dave.

[DBeck]

Re: 97 M3/4/5 running in STU

I run around 33-34 cold in my Dunlop Z1 star specs and never let them above 40 psi. They don't get greasy but you can feel the grip fall off at pressures above 40.

[97M3]

Re: 97 M3/4/5 running in STU

The suspension is TCKline coilover with 450/500 springs and single adjustable Konis. The tires are 245/40-17 Star Specs.

How firm should the shock settings be?

What alignment should we go with THIS Sunday?

Someone throw out their tire pressures they run NOW.

[Redwood]

Re: 97 M3/4/5 running in STU

If it's driven on the street 10%, I would go with Hawk HP+. That seems to be a good autocross pad, with a bit more noise and dust than a regular street pad. Pressures are going to vary based on suspension set up, tire model, etc. You should get or borrow a pyrometer and do some testing of the tire temps and play with the tire pressures if you can find some kind of autocross practice to attend.

[97M3]

Re: 97 M3/4/5 running in STU

We own to general automotive shops in the bay area. This car will be the advertising board for local BMWCCA, SSCA, UFO and local and regional AAS events.

Not removing the interior, already own the 17 X 8.5 Kosei with Dunlop Spec Stars and installed a TCK SA setup with 450/500 springs and plates.

What tire pressures do like to start with. This is were you might consider being specific. I run 43/38 cold with my Z3 running on 01Rs, very neutral with co-driver.

What pads do you like? This car will be driven on the street 10%. The remainder will be spent autocrossing, no track events expected.

Stock bars on the car, stick with them or replace and with what? What settings? My Z3 has H&Rs set medium front and rear for neutral handling.

As for the engine mods, I assume the only legal areas are cold air induction, software and delete fan? I don't see the header helping enough. Cat back system is how much lighter? Worth the expense?

Throw it around a little...

[McCall]

Re: 97 M3/4/5 running in STU

It has the sunroof, Modena leather with Boston Metallic, very rare. Plan to leave the interior intact.

Sounds like you have some self-implemented limitations on the sucess of your new car at being competitive, at least nationally. I agree with Fair, what are your goals? If you just want to show up locally and have fun, sounds like you are done modding. Seat time will help you more than anything else at being competitive. If you want to step up to a National level, that's a whole other thing and Fair layed out a great plan for you. Of course it will start with you buying another car...

[Fair!]

Re: 97 M3/4/5 running in STU

Agaain...

What are your goals - fast at local events, an STU National Championship, or somewhere in between?

[John in Houston]

Re: 97 M3/4/5 running in STU

Can this car be competitive? What else can be done within the rules? Let me have it!

Locally, sure.

Nationally, No.

[Redwood]

Re: 97 M3/4/5 running in STU

I do, but I don't really have much input. Fair has been prepping the race car or racing all weekend.

[97M3]

Re: 97 M3/4/5 running in STU

Hello, does anyone reads these post?

[97M3]

Re: 97 M3/4/5 running in STU

The only mods completed are the strut bar, SA suspension 450/500lb and the RTAB limiters. Everything else is new/serviceable and stock. Plan to drive 6K/yr on the street.

I won't break the rules but do bend them with our Z3 in BS-T1 now. Run 01Rs on the Z3 but chose Star Specs for the M3 4 door 5spd.

It has the sunroof, Modena leather with Boston Metallic, very rare. Plan to leave the interior intact.

Engine has 113K on it. Great compression, smooth idle but no dyno. I expect 225 at the wheels. No software yet. Removed baffle from air box for now but will add cold air kit before next year.

What suspension mods should we do? How big a tire combo can we run without massaging body? ECU software recommendations? Any other recommendations?

Thanks