Guys, you are readking stuff from this post that I didn't mean. Here is the question, that I think Aaron already answered.
This is what we know to be true:
Wider tires, taller tires (sidewalls), softer, less air pressure, get more traction. Weither it be from friction, less force or torque applied, whatever.
Physics - Surface area has flat out nothing to do with the coeficient of friction. If you could successfully prove this wrong you would be one rich fellow and in many textbooks.
BUT
In the real world there is some explaination for why the above factors increase traction. (not sure if I can use friction here)
The material of the tire will change the coefficient. And the cars dynamics has a lot to do with it. (May account for height changes, air pressure).
I read something on the internet, maybe from MMFF, about a guy with a TT 5.0 mustang, that kind of proved/ explained the tire width thing, with launching G's and such.
Breath. Did I miss anything?
It was obviously a good question.
-Julian