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      10-17-2012, 11:31 AM   #14
Kcyrusm
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Drives: 2012 335is DCT
Join Date: Oct 2010
Location: N. VA

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I am not an experienced autocrosser by any means, and have only completed 3 so far, but I just wanted some input on my tire pressure experience. After reading the posts in here, I am way off what people are using, lol...

First off, I drive a 335is and the tire pressure recommendations on the door sill are 33/41 on 225/255's. I guess due to the heavier weight of the 'is'? I'm still running the stock Pilot Sport rft that came with the car, and was blaming my stock tires until I started seeing better times coming out of the same cars. BTW, running traction control fully off.

I set my pressures cold to 36/45 and began my day. Well, after learning the course and learning not to overdrive my car so much, I started shaving lots of time off. Here's the thing, I didn't bother to check my tire pressures as my tires heated up (especially in the fun runs at the end) and I had my best times at the end of those fun runs shaving off another 6/10 of a second.

Out of curiosity and realizing my hadn't checked my pressures in the back to back fun runs, I pulled out my tire gauge. 40/49 f/r. These had my car handling exactly how I wanted. Minimized some of the understeer (which I'm sure a lot had to do with my better lines and not over driving the tires) and let my rear end rotate when I needed it to, in mid-turn with some throttle input.

Was this tire pressure setup crazy??? Should I set these pressures cold next time and start releasing air to keep the same pressures as my tires warm? It was 45 degrees F by the end of the day.

I noticed some of you are running more pressure in the front than rear?