QUOTE(orange914 @ Sep 29 2010, 03:06 PM)
tire size shouldn't factor the pressure at all from anything i've ever heard.
manufacture, wear and use has always been my guide. myself, i max. the tires recommended pressure (within a couple lbs.'s for expansion). on my dd i see a realistic couple mpg's differance (factory digital onboard readout).
just a rant... recently i've battled both americas tires and the ford dealership. they would only put 30psi because (they claim) they have to go with what the factory door tag says.
not the acually tire spec.'s of the tires on the car (44 psi max.)
44psi is the recomended psi to acheive the tires rated max load.
the psi to acheive the best wear and performance would depend on the weight of the car and the size of the tire.
if you inflate the tire to max psi and only have 1/4 of the max weight loading the tires you will be riding on a very small contact patch of the tire.
with the proper psi and contact patch you will have the safest braking [main reason that the dealers won't over inflate your tires] and the best tire wear and the best ride.
over inflating the tires gives you the "feeling" that the tires turn in quicker and better, it kinda does by making them twitchy. but best overall performance is not at max psi.
don't believe me? google it....