Tire Pressure for Autocross - 986 Forum - The Community for Porsche Boxster & Cayman Owners

edevlin · 03-28-2008, 04:11 AM

I know this topic has been discussed somewhat before, but I am trying to get ready for my first autocross tomorrow. I have 18" wheels with PS2's on my base 2000 boxster. I normally run 36/42 lbs for everyday driving, but was wondering what pressure folks would recommend for autocross, thanks,

Ed

:dance:

Topless · 03-28-2008, 07:35 AM

Quote:

Originally Posted by edevlin

I know this topic has been discussed somewhat before, but I am trying to get ready for my first autocross tomorrow. I have 18" wheels with PS2's on my base 2000 boxster. I normally run 36/42 lbs for everyday driving, but was wondering what pressure folks would recommend for autocross, thanks,

Ed

:dance:

Ed,
I'm glad to see you are going cone chasing this weekend. I think you will love it. On tire pressures, if you talk to 10 different drivers you will probably get 10 different ideas. Here's mine:

For the first few days run an extra 5psi over factory settings in each to prevent sidewall rollover (tire damage) as you learn the sport. You are already there. Don't worry too much about lap times at this point. As you get better and smoother you can run less and less pressure and get even better grip without rollover. Ask your instructor to show you how to chalk your tires and check for rollover after each run. Have fun!

D.L. · 03-28-2008, 08:27 AM

That sounds high for some reason for everyday driving... I usually have them at 32/35 for my tires. I would like to hear what anyone else thinks. Have I been driving with low pressure?

edevlin · 03-28-2008, 08:47 AM

"That sounds high for some reason for everyday driving... I usually have them at 32/35 for my tires. I would like to hear what anyone else thinks. Have I been driving with low pressure?"

I actually run 36/40 lbs, not 36/42 as I stated in my post. I went through a set of rear PS2's at 40 lbs and there was no unusual wear on the center of the tire. The higher pressure seems to give me the sidewall stiffness I like. I have had the front PS2's in the mid 30's for over 10K and they hardly show any wear. I will end up going through at least three sets of rear PS2's for one set of front tires.

BTW, I tried using 40 lbs on the rear set of Falken 512 tires I have, and they responded by wearing out more on the center of the tire until I adjusted the pressure down.

Topless, thanks for the advice, it should be fun,

Ed

Sammy · 03-28-2008, 12:30 PM

I run 32 (front) and 36 (rear) for autocrossing with R-compound tires.

racer_d · 03-28-2008, 04:28 PM

With my R comps I ran 36F, 34R. For street tires I tried 38 all around (it was wet/raining) but well.. as someone said, ask 10 people you will get 10 different answers.

If you're really curious, get a pyrometer to check temps and also chalk the shoulder of the tire to check sidewall rollover.

More importantly - have fun chasing some cones! What event are you attending?

edevlin · 03-28-2008, 04:40 PM

I'm attending the Shenandoah PCA/Euroclassics Autocross at RIR, here is a blurb on it:

"Autocross at RIR: Autocross on the NASCAR oval at Richmond International Raceway on March 29! Experience the banked oval at RIR with a fast but safe autocross. There will be two autocross courses—one for practice/warmup on the infield, the other on the banked oval."

Sounds like fun,

Ed

:dance:

racer_d · 03-28-2008, 07:21 PM

Quote:

Originally Posted by edevlin

I'm attending the Shenandoah PCA/Euroclassics Autocross at RIR, here is a blurb on it:

"Autocross at RIR: Autocross on the NASCAR oval at Richmond International Raceway on March 29! Experience the banked oval at RIR with a fast but safe autocross. There will be two autocross courses—one for practice/warmup on the infield, the other on the banked oval."

Sounds like fun,

Ed

:dance:

It does sound like fun... I'll be Instructing at the Potomac PCA Autocross school or else I would have tried to come down!

John V · 03-30-2008, 05:13 PM

My rule of thumb is run as little pressure as the tires will tolerate. However it depends on the surface.

High-grip surfaces require more pressure than low-grip. Hoosier A6s require much higher than Kumho V710s. Street tires in general require higher pressure because of their softer sidewalls.

For Kumhos we like 31-32psi front and rear on medium to low-grip asphalt (like Heartland park, FedEx field, etc) and low-grip concrete like Toledo. When we try Hoosiers this year, probably 38psi all around to start due to the weaker sidewalls of the A6.

This on a 2000 S weighing 2900lbs(ish) with 245/35/18 on 7.5" front wheels and 285/30/18 on 9" rear wheels.