Cause for tire cupping?

[OverlandZJ]

Just had my tires rebalanced and rotated front to rear. I had an annoying hum that i first thought was a unitized wheel bearing, which were replaced last week. Still had the noise.

When they rotated the tires the hum stopped in the front. And started in the rear.

Looking at the tires they do have a little cupping to them which is causing the noise. But what caused the cupping?

[njtaco]

IMHO, Alignment, Shock absorbers,Tire pressure, probably in that order.

[smbisig]

Just had my tires rebalanced and rotated front to rear. I had an annoying hum that i first thought was a unitized wheel bearing, which were replaced last week. Still had the noise.

When they rotated the tires the hum stopped in the front. And started in the rear.

Looking at the tires they do have a little cupping to them which is causing the noise. But what caused the cupping?

What kind brand/model tires?

[flyingwil]

Tire pressure is the #1 cause for tire cupping as far as I know... I try and balance them out, I typically run at 32psi, then to prevent cupping, I run at 35 PSI for about 3 weeks after each rotation and balance.

[CLynn85]

Low tire pressure usually results in cupping. Had that a few times with my stock GSA's. Everytime the pressure was low.

[OverlandZJ]

Going to check presure again today, i usually run at 32 PSI. I have a run to the Pa Grand Canyon friday through sunday....then a quik run to SC sun night thru tuesday. I'll run 35 PSI all weekend.

Also going to check my toe again.

These are 33x12.5x15 BFG MT's.

Thanks Guys.

[njtaco]

Have you been rotating the tires regularly? 3K-5K intervals? This would help even out any cupping before it got bad enough to hear or feel.

Also, you would not be the first to chage bearings out due to a tire noise. I've seen very experienced mechanics chase tire noise around, and change unit bearings for the same reasons you did. More than a few "alignment issues" have been resolved by tire rotation, too. Like pulling to one side or another, wander, etc.

[OverlandZJ]

njtaco...admittedly i'm probably over the 5k mark on the rotation.

I have a bud who kept experiencing cupping, even with frequent rotation. It didnt stop till he replaced the leaf springs...this was on a Wrangler. Which has me thinking...

I redid the entire front suspension on my Cherokee last year. Switched to a longarm assembly. I'm going to get this Jeep on a good laser rack and check all the measurements. Bet somethings off.

Thanks for the input guys!

[OverlandZJ]

The drive to SC went smooth, rotating the cupped tires to the rear took away the slight vibe.