[mbtoloczko]

Originally posted by lee
wheel size isn't important, but rolling radius of the tire is VERY important.

here's how to set it up regardless of what a tire guy tells you:

set EITHER the front, or back, tires at the pressure you want. then adjust the air pressure in the tires at the other end so the distance from ground to the middle of the wheel is the same.

So in my car with 225X50X16 Fulda tires I have the back set at 30PSI. The I adjusted air pressure in the front until the distance measured at the middle was the same. Turned out I need 41PSI in front.

If you really wanted to be up-tight about it, you could chalk mark the tires and adjust pressure until they rolled the same number of revolutions (in a straight line of course).

....

I swear I'm not up-tight, but I did chalk the tires (white-out actually) and measure the revolutions with the front and rear tires at various pressures. What I found is that for identical tires in the front and rear, when the front and rear tires have the same loaded radius, the rolling circumference is different. The front will have a larger rolling circumference even though the loaded radius is the same as the rear, at least that's what I observed. I did the measurement several times to verify. I've got a posting on the network on the measurements. The best I could figure is that other factors such as toe and camber are playing a role.