What Causes Tire Cupping on the Inside Tire of a Dual Wheel Setup

Published 09/06/2018

Question:

I have a 40’ PJ trailer dual axel and dual wheels. I have only 1 tire, back axel passenger side inner tire that is cupping and scalloping horriblly and it’s the only tire doing so. Could it be bearings? Suspension? Alignment? The tire in front of it outer tire isn’t damaged like the inner tire. What can it be?

asked by: Gomez

Expert Reply:

There could be several different causes for the tire cupping. Since it is only happening on the inner tire of your dual tire setup, have you checked the air pressure in the tire? If the air pressure is different between the two tires this could very likely be the cause of your cupping problem which means the tire is bouncing. The tires will need to be filled to the max psi listed on the sidewall.

If you have checked the air pressure then another potential cause is the balance of the wheel/tire. If the wheel/tire is out of balance more so than normal as trailers typically have a higher tolerance for out of balance wheels/tires then this could also be a cause of the tire cupping issue you are having.

The other potential cause is a worn out suspension. If the leaf springs, shackle straps, or equalizers look worn or damaged then they will need to be replaced. Let me know what you come back with and if there are any parts you need to help correct the issue. You may also want to take the trailer to a specialty shop to see if they can check the alignment of the axles for you.

expert reply by: Conner L