E46Fanatics - View Single Post - Got to know my E46 a little better. (Autocross)
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Old 10-08-2012, 10:51 PM   #44
peytonracer4's Avatar
Join Date: Jan 2010
Location: Valparaiso, IN
Posts: 7,755
My Ride: '00 328i
Originally Posted by dmax View Post
I'm confused then. I have eliminated my understeer by keeping my front tires at the maximum door jamb pressure (32) and the rears in the towards the low/middle side of pressure.

I don't have understeer...mine it pretty neutral right now. When I apply gas lightly through turns, I push out the rear end and definitely notice throttle steering.

You might increase the throttle steering response with higher pressure, but a little more pressure does make the tire diameter greater, and thus the same angle of steering causes more turning.

This is what I've read in many places and have direct experience with...just saying.

Mango, I agree, though, that I bet a lot of time has to do with contact patch and that using door jamb, even at autoX might be better than 40 all around (though that might be closer to your recommended pressures than mine). I'm 29-32 in front and 33-41 in rear (I think).
doug i'm going to have to complete disagree with you here. you haven't eliminated your understeer. tire pressure alone will not eliminate understeer. you will need to dial in several other modifications to get your car neutral. it's very hard to do.
also the pressures on the door jambs are NOT recommended for autocross. when you're cornering under extreme conditions your tire gets much more force than under street driving. you cannot drive as hard on the street as you do in autocross. i don't care who you are and where you drive you just can't do it.
in his original pictures you can see the tire tread patch. then you can see slight wear on the outsides of that. that is a sign the tire did not have enough pressure to deal with the force it had on it and needs to be increased. the tire will flatten the more weight you put on it and the sides will start to "roll over"
he should be running at least 40 psi. at my autocross yesterday i ran about 41 all around and still had slight rubbing outside of the tread patch. anywhere outside of that tread patch is considered to have zero grip.
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