I know this is strictly based on your application and selected tires, But does anybody else notice that (at least on my 318 / 4X4) that the tires need to be around 33 -35? I know that the manual and the sticker on the door requests 32. But when I run them that low I seem to get bad outside cupping on the tires. I have replaced all four ball joints with Moogs problem solvers and that didnt stop the cupping.

 

Your front or all 4 tires?

Your right, it varies a lot. I will never run a correctly chosen truck tire more than 10 psi below its max. IE if my truck runs tires that are 50 psi max I usually run them around 40. Any softer than that and I usualy get wear issues.

 

Your tires has a max air pressure. Go by that not the door jam. Also depending how the wear is it may be an aliment issue.

 

Take Chalk make a line across the tire. Drive forward a bit and then adjust pressure from there. (if your like me and live out in the sticks where there arn't paved roads ffor a ways then do it in town at a gas station that has air.


Josh

 

Not true!!!!!!!!!! That max psi is a number the tire company puts on the tire telling what the tire can handle before failure without knowing what kind of vehicle the tire is going to go on. You need to put in the correct amount of pressure for the weight of your vehicle and desired footprint of the tire... If you put too much air in the tire you'll wear out the center of the tread cause the footprint will be smaller. If you put too little air in the tire it will wear the outer edge of the tire out faster cause it will need too big of a footprint and bubble out.

Basically the pressure in psi of the tire is self explanatory. The tire is supposed to have a certain footprint to maintain a balanced weight distribution across the tread. The psi (pounds per square inch) you put in the tire needs to be directly related to the desired footprint of the tire and the weight of the vehicle its going in. If you are running factory tires, use the pressure listed in the door jamb cause it is calibrated by the factory. If you have added a lot of extra weight to the truck or are using a different than factory tire size, you need to adjust the pressure accordingly. Basically, if you are using a bigger tire, it will have a bigger footprint, so you have more square inches and the same number of pounds, so psi needs to drop. If you are adding more weight to the truck, you have more pounds, which will force the tire to have a bigger footprint... you need to come back to the correct footprint in square inches, so psi needs to increase.

The only way to know for sure the correct pressure for your application if it is no longer factory is to measure the desired footprint of the tire, weigh the truck and do the math. Factory is 35 psi for my truck... I run 32 psi in each tire since they are bigger than factory and I haven't had a single problem with irregular wear.

 

perfect! couldn't have said it any better myself...

also, one other factor in cupping outer treads is shocks, they will cause it too, if they are old, you might think about changing