Toy_Guy

<center><img src="http://pictureposter.audiworld.com/AudiWorldPics/2000/craigs/tiregrip.jpg"></center><p>I had been wondering why the track drivers say ADD air to the rear tires, and others say REMOVE air from the rear tires in order to minimize understeer. I think I have a pretty good explanation here:

There is an optimum tire inflation pressure which will maximize cornering grip (refer to image). This is what I refer to as the track inflation pressure. For normal street driving, the pressures are set much lower in order to preserve some ride comfort and increase the tread life.

When we want to minize understeer by making adjustments to tire pressure, we need to shift the balance to more grip in the front/less grip in the rear.

Thus, the adjustment to the normal street inflation is to increase pressure in the front tire (increase grip) and reduce pressure in the rears (reduce grip).

We have a different scenario with the track setup. The front tires are already at max grip, and so cannot be improved further. The only adjustment is to reduce the grip of the rear tires. The pressure can be increased OR reduced away from the optimum. But in practice, the pressure is increased for better tire life.

I would appreciate any comments.

:::EuroRacerGT:::

sounds good!

Wayne H.

In fact, I posted a similar comment awhile back.

4kq

The traction curve for tires is a hump with a low angle on the low pressure side and a steeper angle an the high pressure side. You can get any tire to lose traction with EITHER more or less air. Less air allows folding of tire, more air acts like additional spring rate and creates a more curved tire profile.

For oversteer, the rears get more air because an underinflated tire will fail catastrophically at the worst time.

BRD

To minimize understeer, increase pressures in front and reduce in rear. Depending on tires (street or track) the fronts should be 2-4 psi higher. I have extensive track experience and this always works. This is the only correct answer. It is basic vehicle dynamics that they teach at any racing or driving school!