Michelin Load & Inflation Tables

[davidbrady]

You'd definitely see an improvement in ride quality by going to 315's everywhere. If I got the load tables right your steer axle pressures would drop from 105 to less than 95 psi and your drives would drop from 100 to less than 90 psi. (These are rough estimate numbers).

A wheels dual spacing is completely dependent upon the wheels outset dimension. Double the outset to get the wheel spacing. For the 8.25" Alcoa wheel the outset is 6.6 inches. Doubling this gives us the wheel spacing measurement that you found earlier of 13.2", which we know isn't quite enough if you're going by the book.

Alcoa does allow a high temperature nylon spacer to be used between aluminum and steel wheels and between aluminum wheels and steel drums. I don't have one in front of me but I'd guess the thickness to be as much as 0.10" which would bring your spacing to 13.3. I'd get on the phone with Alcoa to see what the actual thickness of the spacer is and what their recommendation might be, or maybe someone here has a spacer in front of them.

Amendment: Well, looks like I didn't get the load tables right. The pressure numbers that I cite above are for the LRL 315/80R22.5" Michelin tire on a 9.0" wheel. On an 8.25" wheel mrkane's steer pressures drop to 101.5 psi and his drive tires drop to about 90 psi. Still a good ride improvement, but not quite as dramatic on the steers. (Thanks mbulriss)!