Tire pressure

[carperformance3]

okay, i've been toying around with my tire pressures on my 3 for the last 3 or 4 months, but i've by far made the most progression today, when i went autocrossing for the 2nd time. granted some people don't want their car set up for maximum performance at any cost, and different courses will warrent slightly different tire pressure needs. but i found a very useful tire pressure setting. if any of you have heard of putting shoe polish on your sidewalls to watch rollover, this is how i found my pressure. wanting to save my all-season tires from the destruction of autoxing i started today with 42.5 in the front, and 41 in the rear. if you look on the corners of your tires there is a little arrow every so many grooves. when you put the shoe polish on, your goal is to get the tires to rollover to the tip of that arrow. any more rollover than that, and its counter productive. so what i found in my testing today, my final tire pressure (when hot), was 46 psi in the front, and 34 psi in the rear. yes, you read that right, very drastic, but without suspension mods, the rear just doesn't do a whole lot on the 3 other than hold on. i actually could have gotten away with even lower pressure in the rear, but that was my last run, and i was dropping them about 2 psi per run (versus start of previous run). if you doubt my credibility on these numbers, i beat two sti's, one of them modified, a heavily modified s2000, about 2 seconds behind a heavily modified evo, and i beat my friend in an integra type r. and all i have is an intake. those pressures when cold, based on the amount of air i released from the front (which were still rolling over too much) would be sitting about 42 cold, and about 30 in the rear. i'm not done playing yet, although i must admit, i did drop my front tire pressure some when i left, because i noticed the center of my tread wearing faster than the corners (surprisingly). more or less the moral of the story is if you want max performance by adjusting your tire pressure (cheapest way to get it), you're going to want some pretty drastic pressure differances.