What cause "scallops" on all position tires on front axles?

opus · March 23, 2015, 11:13:14 AM

I had that, replaced shocks and that cured it.

TomC · March 23, 2015, 11:19:41 AM

If you're running all position tires without the decupler groove on the side of the tire, around 60,000mi, you'll start to get this kind of tire wear. You should have line haul steer tires on the front if you want to get more than 50 or 60,000 miles out of the tires. Good Luck, TomC

belfert · March 23, 2015, 05:24:08 PM

Current set of steer tires has less than 20,000 miles on them. The set before that I got maybe 30,000 miles out of them.

TomC · March 24, 2015, 08:19:09 AM

I had a customer with a new Freightliner that had a truck do exactly this. It was cured by a complete all axle alignment. Good Luck, TomC

Jim Eh. · March 24, 2015, 09:51:39 AM

We found if the rears are out of alignment the steers would wear both on the same side ( both on the curb side usually) and wear off smoothly but not scallop both edges.

belfert · March 26, 2015, 09:57:31 PM

I had the rear aligned within the past two years. I don't recall if the front was checked or not at the time.

belfert · March 29, 2015, 03:40:36 PM

I finally had a chance to look more closely at the tires on Friday. They aren't as bad as I originally thought. The wear isn't nearly as bad yet as the last set of tires that I had to replace due to this same issue. The tires are probably salvageable if the problem causing the strange wear can be fixed.

I have attached photos of the tires. The problem is on the inside edge of both front tires. I took the picture from a different direction on the driver's side tire.

luvrbus · March 29, 2015, 05:23:04 PM

That is caused by negative camber not shocks it is caused most of the time by worn king pins or upper a frame bushings letting the wheel lean in on the top that may cost you some bucks to remedy

Once the tire has that wear pattern there no stopping it looks like you have spare a set for the tag now

good luck

Jim Eh. · March 29, 2015, 06:37:36 PM

Ditto on the tire wear memory. Try a simple toe in check with a tape measure. You may find you are toed out. Does it tend to wander or dart one way or the other especially on an asphalt roads?

belfert · March 31, 2015, 05:47:01 PM

I talked to JD over at C&J Bus Repair about this today. He has seen this exact issue before and he doesn't think it is king pins. He says the tires are just bad, or it could be toe-in.

I looked through my maintenance manual today and it didn't really clear much up. You would think replacing the king pins is easy if you read the book, but I know it is a long process even for an experienced shop.

eagle19952 · March 31, 2015, 05:55:35 PM

Quote from: belfert on March 31, 2015, 05:47:01 PM
He says the tires are just bad,

i have had this happen on tires that were fine and developed scallops with years and miles on them.

the just bad argument makes no sense to me
.

twostick · March 31, 2015, 06:17:02 PM

Inside wear I would suspect toe out. No de-coupler grooves don't help but that usually causes outside wear too.

I run 12r22.5's on the front of my highway truck. Nobody makes a 12r with a decoupler so I get that kind of wear on the outside and some on the inside. Lucky to get 100,000 mi out of a set.

It's not king pins as that usually appears as several diagonal bands of wear across the face of the tire. Bad or loose wheel bearings can cause similar wear as king pins.

What size and brand of tire?

Kevin

TomC · April 01, 2015, 07:19:35 AM

Kevin-next set, switch to 315/80R-22.5 tires. They are the metric equivalent of the 12R-22.5, but have 18,000lb rating. Many tire manufacturers are making highway steer tires. The 315 is the popular tire in Europe since their axle weights are higher than ours. Most new buses are using the 315 (even 365's) since they are getting heavier. Good Luck, TomC

belfert · April 02, 2015, 03:31:51 PM

I sure the heck hope I don't need upper control arm bushings. They are $620 each! I would need four to replace them on both sides.

belfert · May 05, 2015, 08:01:44 AM

I finally got the bus in to get this tire issue looked at. The service place did an alignment and found the toe was out by 1/8". The guys at Precision Frame in Elk River, MN thought it was the tire and recommended I go back to the tire dealer. The tire dealer said it is not the tire. He pulled out a book and showed me a picture of the exact problem I am having. The book said low tire pressures and bad shocks are two possible causes. I said I run the proper tire pressures by weight. The tire guy still recommended increasing the pressure.

Nobody said there is any problem running the tire for now. They did recommend swapping the left and right tires. I will get new steer tires in a year or two and swap the current steer tires back to the tags axle. i will probably replace front shocks since they are fairly inexpensive.