Not quite that simple. (more, long explanation) (archive)

You could also wonder, I suppose why, in a nearly 50/50 balanced car, stock spring weights in the front around around 115lbs/in and 340lbs/in in the rear. Typically, making rear springs stiffer dials oversteer, so you'd expect the M3 to oversteer like crazy, right?

The point is there are a lot of factors that act on the car the engineers take into account, and a few factors taken by themselves may seem to contradict textbook definitions of car handling, until you know them all. I certainly don't! :)

From experience I can tell you running street tires at 29 front, 33 rear will give you a bit of oversteer. I personally run pretty similar pressures front and rear on the street, (slightly less oversteer) and 3-4 lbs higher in the front autocrossing (43 front, 39 rear), which oversteers less.

Now, most textbooks will show you a chart that says something like:

rear tire pressure higher = more bias toward understeer
rear tire pressure lower = more bias toward oversteer

All of this can vary, however, with tire type, suspension components, bias of the suspension components front to rear, if the turn is transition, if it's constant, etc. I say, the BMW guys built the durn thing, they probably know what they're doing. But it doesn't hurt to play with tire pressure a little bit and see how the car changes temperment.

Just be sure to experiment where there's no chance of having some newfound oversteer spin you off the road...

Andy -- '97 M3

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