The equation still holds. As the tire deforms to have more area the pressure on any particular part of the tire is lower. The total friction is unchanged. > Th

The equation still holds. As the tire deforms to have more area the pressure on any particular part of the tire is lower. The total friction is unchanged. > That is why you see racing cars with big fat tires If you mean drag racers those tires are glued to the ground, and do not work off of friction. Other than that, what race cars have big fat tires? Tires are usually sized so that the ground pressure of the tire is in the 40 to 100 psi range (which is also the tire inflation pressure). That's simply to keep the ground from deforming and the tire from popping. It does not affect friction. This is also why off-road tires have lower pressure - the sand and mud they work on is not strong enough for a higher pressure. It is NOT for increased friction, it's because the surface they drive on can't handle it, so you spread out the weight, and reduce the pressure.