I have some 36 x 13.5 x 16 bias-ply iroks on my 99 f150 w/ 4.2 running @ 30 psi. After 3k miles they have worn very fast in the center particularly the front ones. After contacting interco which told me to run them at 35 psi I was a bit confused and asked them why I would raise the pressure when they are wearing horribly in the center as it is. They then told me to just play around with the pressure until it looks right. So I dropped the pressure to ~25-27psi. As of last week I just found out my upper/lower ball joints were shot so im guessing that has a lot to do with the wear on the front tires? Considering that takes care of the problem do you guys have any input on what pressure to run these things at? I understand they arent a long lasting tire but the inside of the center 2 lugs have already worn down between 1/8 - 1/4".

 

I believe Interco's original instructions were correct ...

imo, The problem is not that the tire is riding in the middle, it is riding on the highest edge which happens to be the middle because your truck does not weight enough to compress the outer edge of the tire and how the torsion bar system works vs. straight front axle.

The real solution would be to more backspacing, but, your truck does not have enough wheel well for that.

What to do is get a roll of masking paper and drive the truck over a length of 12 feet or so. Rip the paper from behind the front tires and see what kind of pattern JUST the front makes.

Increase the pressure, try again. Lower to 25 psi and try again. See which increases the outer shoulder pattern. If you have trouble telling, push a tack into the outer shoulder and see which dents the paper more.

> As of last week I just found out my upper/lower ball joints were shot so im
> guessing that has a lot to do with the wear on the front tires?

I would say no, but, the tires might have something to do with the balljoints going.

> do you guys have any input on what pressure to run these things at?

I would not run them any lower then 25 psi at highway speeds, except in winter, I would stick to at least 32 psi.

Rotate the tires frequently, that is the only way to make the tires laster longer.

What you might try is loosening the torsion bars a bit and see if that helps the tire wear.

imo, You have more tire then truck and I would expect to be doing front end work on a regular basis, say once a year.

If the future, you might want to switch back to a radial.