Originally Posted by ChrisRX8PR

LionZoo,
You are absolutely right about the fact that if you keep the weight the same and increase the size of the tire it will deform a little less because it is a wider tire and the weight is distributed alond a wider surface therefore the width of the contact patch is reduced slightly. The contact area should stay the same in theory but this is not the case in reality. As soon as the car moves the contact patch changes due to weight transfer etc. You also add tire pressure to the equation and it gets very complicated very fast because reducing the pressure effectively increases the contact patch aread because the tire flatens a little.
What I am trying to get at is that the tire is round meaning that if the contact patch is a rectangle pressure is nor distributed evenly across it, it is concentrated more towards the center line of this rectagle(line going widthwise across center of contact patch) because the tire is trying to stay round and this is where it exerts its most of its force. This means that the more area that you have close to this centerline(widthwise on the tire) the more effective the weight will be used to generate friction with the ground(smaller slip angle because you're closer to the theoretical contact line between the tire and the surface). This makes the longer, thinner contact patch of the wider tire more desirable for power transmision because althought in theory its contact area might be the same as the thinner tire's, it is more concentrated towards the place where most of the force is being excerted. The fact that the tire is wider also allows you to use less tire pressure for a given car weiht in turn widening the contact patch to match the width with a thinner tire therefore increasing total contact patch area.
I am not saying in any way that wider in rear is always better, as a matter of fact a factory rx8 would probably not benefit from this, it would probably cause it to understeer and loose speed due to weight too. I am just stating the reason that wider allows you more transfer of power in a straightline even if in theory the contact patch stays the same. I know this for a fact because I had to do a 1 year study on this matter as a final graduation project to my engineering degree and these were my findings after doing a lot of research and speaking to some of the senior design engineers at brigestone and goodyear.
I hope you are not offended in any way with this comment, I just wanted to post my findings, not discredit your statement.