he ask what is the common psi what most run .... but on the simple physics please do post the mathmatical formula behind ur thinking.... that being said my thoughts were if the sidwalls have enough pressure to properly inflate them the resitance from the tread would be the same .... so by your physics if i buy i tire with sam tread compound thats rated for 100psi and buy the same rated for 40 the 100 psi will get better gas milige.... i think theres a hole in your physics.... but if im wrong plese do post the math formula....
