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      09-25-2013, 10:33 PM   #1
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mmurray's Avatar

Drives: E90 330xi
Join Date: Feb 2013
Location: South NJ, USA

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Autocross Tire Pressure Questions

As I've learned, a little background goes a long way - On advice from my first few autoX events, I was running slightly higher tire pressures than factory recco (around 4 psi higher up front, plus an extra few for 6psi in the rear - the idea being that I'd get some oversteer back on my XI with the difference, so I was told).

As the season progressed and I started getting consistent, I began to see the effects of a cool/ warmed/ hot/ and overheated tire on my times throughout the day. Best runs were on warm days in the afternoon of split sessions (warm but not gone - thinking of buying a sprayer, will that help?).

The real issue I'm experiencing now is a LOT of sidewall roll on the fronts. I'm running stock staggered 225/40-18, 255/25-18 Bridgestone RE760s (RTA) and have seen marks come to within 3/4" of the wheel itself (pressures were good, checked with a gauge between runs, and against a compressor at the break). I even started pushing my psi limits in hopes of compensating, but no luck.

Suggestions have been to wrap more 255s over the front wheels to square up, but I'd like to explore other options before making that jump with my DD.

Any ideas/ suggestions/ advice? Thanks
Keep right, except to pass. // Mystic E90 330xi 6MT - ZSP/ZPP/ZCW
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      09-25-2013, 11:48 PM   #2
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Those tires have soft sidewalls, so that's not surprising. What pressures exactly are you running?
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      09-26-2013, 10:35 AM   #3

Drives: 335i LCI
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Do not compensate for a soft sidewall with tire pressure, add camber instead if you are rolling the sidewall that much.

Pressures I run 2.3 front (OEM) and 2.5 rear (less than OEM)
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