Thursday, September 24, 2015

Tire Tread Wear

One normally sees abnormal tire tread wear on the front tires, where there are more places for something to get out of kilter affecting toe-in, camber, etc. Rear axles are presumed to be less of a problem. But a LD owner Mike Coachman recently discovered that there can be an issue with the rear axle:

On the original Michelin tire set and more recently on the second set of Michelins the inside 3”+ of tread (closest to the differential) of the inside dual tires on both sides had worn considerably more than the rest of the tread. The outside dual tires showed even wear equal to the remaining tread on the tires in question. The Bilstiein shocks appeared to be in good condition (no leaking oil/ good rubber grommets).  Traveling gross weight is +/- 13,280-lbs.(front: 4080-lbs; rear: 9200-lbs -which is within gross weight rating -9500lb- of each axle).   Rear axle tire pressure was maintained at 75-lbs and the front at 60-lbs per the LD owner’s manual.  The owner tows a Honda CRV. Current mileage: 71,000-mi.

Mike took the motorhome to American Frame & Axle in Tampa, FL, for an evaluation of the tire wear problem described above.. Upon inspection they found that both axle housings were equally out of  camber by 0.4 degrees upward.  This explains the tire wear. Toe in/out was ok. Both wheel bearings were turning in their housing. The co-owner & service manager stated that these problems are now common with solid axles of every size vehicle up to the largest of semi tractors/trailers and has been so for about the last 25 years. Prior to that it was rare to find an axle out of true alignment. He attested it to poor manufacturing quality control. If it had been caused by overloading of the axle or severe shock on the road, the out of alignment would not have been equal as was found. The service manager said it was better to fix the axle than replacing it. He said that often a new replacement axle can have the same (or worse) problem.

The rear axle was removed, placed in a press made specifically for this purpose and re-aligned. Bearings were replaced, the axle housings were re-welded to the differential housing, and a complete front to back axle/wheel alignment was completed. The worn tires were rotated to the outside position. Even though this was a manufacturing problem, this coach was well out of warranty. 

Contributor: Mike Coachman

Submitted: 24 Sep 2015