trackday setup question

[enzoaus]

Hi all,

as posted i have following setup on my Z4M Coupe:

KW Suspension with ~500/600 lbs (linear)
F: ~3° R: ~2° camber
F: ~0°2' R: ~0°6' toe (sum)
original anti rollbars

the car is good on corner entrance and exit but the midcorner speed is not at an optimum ... on different semislicks ... (e.g. R888R, Cup2 ...)

what could be the problem ? is it recommended to change der anti rollbar when you change the springrates ​?

thx for help vom Austria (no kangaroo )

Enzo

[Michael9218]

Are your dampers adjustable? Changes in rebound and compression damping could be what is needed.

[enzoaus]

Originally Posted by Michael9218

Are your dampers adjustable? Changes in rebound and compression damping could be what is needed.

sure, i have KW dampers with rebound and compression, to my opinion they are configured good ... (F: 2 cl. compr 4 rebound, R: 3 cl. compr 5 rebound)...

thx eric

[///Mcoupe]

If I was in your place, next time you go to the track, ask an experienced driving instructor to drive your car and talk to him about it. He should be able to pinpoint the cause.

[bwright657]

Originally Posted by ///Mcoupe

If I was in your place, next time you go to the track, ask an experienced driving instructor to drive your car and talk to him about it. He should be able to pinpoint the cause.

Second for this. I could not get any rear end grip in a corner at a track day last year and could not figure out how to remedy it. A buddy of mine who's a test driver for Michelin took it out and diagnosed the the issue as the tire sidewall folding over right away. Added 2psi of air to the rears and then the car would not let go.

At your next track day ask around with the instructors and see if someone can help you dial in your setup. If you're happy with corner entry and corner exit, then you're likely down to fine tuning the dampeners.

[lelandr]

Originally Posted by bwright657

A buddy of mine who's a test driver for Michelin took it out and diagnosed the the issue as the tire sidewall folding over right away. Added 2psi of air to the rears and then the car would not let go.

With respect to this, all of these track and 200TW tires have a specified HOT pressure at which the tires work best. Usually something like 37-39 psi (2.5-2.7bar für unser Österreicher). As you noted, this pressure should optimize the contact patch for track use. I know that when I used RA-1s on my M3, Toyo said 37-38, and Michelin suggests the same for the BFG Rival.

Note that this means that if it is cold or raining (basically a normal summer day in central Europe), that you are going to have to INCREASE your pressures to guarantee the target hot temperature.

I might have run across your buddy. She has since moved on, but AFAIK, my younger sister has been Michelin's only female test driver in NA.

[Vanne]

Very stupid question... Do you have traction control on?
And separate to my above question...
(39 psi?? Wait.. what????... This is absolutely waaaaay to high..)

Nothing wrong with Kangaroos Enzo, as long as you dont get them on your hood.

[lelandr]

Originally Posted by Vanne

(39 psi?? Wait.. what????... This is absolutely waaaaay to high..)

That is the hot pressure (tires at full operating temp). Take the pressure right after you get off track. Depending on your car and skill level, this could be anywhere from 28-32 psi cold. Again, those hot pressures are from Toyo and Michelin directly--I didn't make them up.

The reason that the manufacturers are specifying a hot pressure are as follows:
1. Hot temperatures are the operating temperature. This is the temperature which optimizes the contact patch, sidewall roll-over and the compound's ability to grip.
2. Setting your cold pressures to 32psi on a freezing day is going to yield a different hot pressure than 32psi on a 90deg day.
3. Hot pressures will be affected by driving style, course material and temperature and whether it's wet or not.

[Vanne]

You should be deflating again after coming off the track a few laps, pull in and deflate again to around 28-29, do this twice and then get on it. Unless you have a real time tpms system your not going to know your running hot psi values. 28 is a great starting point.

If your running with traction control on, you won't be getting ANY mid corner performance, or any corner performance for that matter.