[dietrite]

I autocross my 968's and I am having trouble getting the right tire pressure. Does anyone else out there ax there car? If so, what pressure to you find work the best.
Thanks, Paul

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[flash]

there is no guide here - every situation is different, even on the same car but on different days - autocross is really hard, because you never really get the tires hot like you would on the track, but the turns are often tighter

different tires will result in different pressures

different courses will result in different pressures

different ambient temperatures will result in different pressures

different surfaces will result in different pressures

you get the idea

you need to measure the tire temps and look at the wear pattern via "chalking" or something like that - look for the best and most even wear, and the most consistent temps side to side across the tread - then balance that against slippage and roll

sorry - it will take some time and experimentation - i suggest a big parking lot early on a sunday morning

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[bob blackwell]

Well, all of those things are true that "flash" mentions. Still, I find that a good starting point for my 968, using Yokohama S Drive tires, is to add pressure from 35 psi all around (daily driving) to 38 psi all around. You don't even have to "chalk" the tires or mark them with liquid shoe polish to detect where the "scrub mark" is after an autocross run. Just examine the edge of the tires before you start your run and than again after you complete your run, there will be a visible scuff line around the edge of the tire. You want the tire to roll over about 1/8 of an inch to 1/4 of an inch from the tread down on the sidewall. Too much pressure will leave less of a wear pattern (lower by one psi increment); Too little pressure will leave a larger wear pattern (increase by one psi increment). Good luck, it's fun to experiment until you get just what you want! Bob Blackwell.

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[flash]

yeah - autocross is a weird animal - i'm surprised that you raised the pressures though - i would have thought that would have created a pretty slippery situation - it always has on any other car i've messed with - but, i haven't autocrossed this one either

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[JWahlsten]

I used to raise the pressures on my 944 turbo too. Otherwise the sidewalls would roll too much. The turbo was a poor auto-x car with all the lag though. I did learn a good bit about left foot braking however.

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[dietrite]

Interesting, I hadn't thought of equal pressure. Usual advise is more or less, front or rear.
Thanks for the feedback
Paul

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