Tire Pressures for Autocross in a 430

I autocross alot and I don't think it is really worth your time to play with the air pressures. It won't make that much difference in your times. You'll learn more by walking the course and figuring out the quick way thru it.

Adding air pressure is an attempt to stiffen the side walls of the tires so they won't roll over as much. But like you said your side walls are stiff already with low profile tires.

Remember the key is to be smooth. Smooth is fast.

Good luck.

 

Walk the course as much as you can! You also don't have to put air in your tire, but I would check the pressure before you start to race, and after a couple of runs.

Smooth is fast, always look ahead, have fun, and post a vid ;P

 

Um, just say "no" to autocross.

Bad for the brain, bad for the soul, bad for the car.

 

How do you figure that? I'm a pretty avid autocrosser. Done nothing but wonders for me and my driving. Especially for novice drivers it should help add an element of precision in car control that might be lost by driving only large tracks. Also an amazing way to learn to adapt to and memorize tracks vey quickly.

 

The tried-and-tested quick-and-dirty method for determining correct tire pressures for autocross on street tires is to chalk the sidewalls. Rub some chalk threee or four places around the sidewall up to the tread. That makes it easy to see how far the tire is rolling under after your first run, and you can adjust pressures accordingly.

I think you'll find that a few more pounds than standard will be in order, even on low-profile tires. Modern radials don't deform that much under increased pressure, so you don't lose much contact patch that way, but the sidewalls do deform a lot under heavy cornering loads. No matter how aggressive they might be, street tires are still a compromise compared to race tires as far as sidewall stiffness.

 

Scot's got it right. Start with 4-6 psi more than OE recommendations and you can use white shoe polish at the edge of the treadblocks two or three places around the tire.

-Peter (have autocrossed fine 308's, a Daytona and a TR twenty years ago, with success!)