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

belfert · March 20, 2015, 07:18:10 PM

Both of my front tires have these "scallops" in part of the tread. It looks like someone literally took a knife to the tire and cut off chunks of the tread. These are all position tires so they have like rings of treads around the tire. The issue is happening on the second ring of tread in. The tires are not wearing on the edges so I don't think alignment is an issue. Right tire is far worse than the left tire. Any ideas what would cause this?

This is the second set of all position tires in the front that have done this on at least one tire. The current front tires are two or three years old. Two different brands of tires. I want to get any issues fixed before spending another $800 to $1000 on a set of tires. The first set of tires the local tire dealer said the installer put the tires on wrong. It has to be an issue with the bus if this happened twice now.

luvrbus · March 20, 2015, 07:48:49 PM

Worn front end parts probably or you could try a set of steer tires with the anti cupping groves

bevans6 · March 21, 2015, 03:27:51 AM

When it happened to me on other vehicles it was worn out front shocks. At least, the shocks were stock, shot, and the tires didn't cup again after I changed them.

Brian

gumpy · March 21, 2015, 05:09:28 AM

It's pretty hard to "put the tires on wrong". They mount to the rim only one way. They should be balanced. They bolt to the hub only one way.

There are a number of potential causes. Alignment, low air pressure and worn shocks are probably the most likely, but worn king pins, bearings, spindles and
tie rods could all play a contributing factor. Take it to a front end alignment specialist. There's one in Elk River that has a good reputation, I think.

I ran my air pressure according to the mfg chart for the weight on the axle, and they cupped badly. I increased the pressure on the current
set and so far I'm not seeing any similar wear.

Once it starts, it creates an oscillation that just make it continue to worsen. When you get the problem fixed and replace them, run them on the tag axle
where they will scrub off the wear patterns.

Jim Eh. · March 21, 2015, 06:27:51 AM

What kind of feedback do you get thru the steering wheel. Any kind of "speed wobble"?
Have you checked out the front end suspension and steering components?
If you are out and about near a scale check the balance weight of your unit. What are the axle weights?
A TPMS system is helpful although a tad expensive but then again tires are cheap ... right?

eagle19952 · March 21, 2015, 08:19:34 AM

They mount to the rim only one way...
not true...lots of tires are uni-directional.

Jim Eh. · March 21, 2015, 08:47:45 AM

Any directional tire will have arrows clearly molded into the sidewall.

belfert · March 21, 2015, 06:45:49 PM

Quote from: krank on March 21, 2015, 06:27:51 AM
What kind of feedback do you get thru the steering wheel. Any kind of "speed wobble"?
Have you checked out the front end suspension and steering components?
If you are out and about near a scale check the balance weight of your unit. What are the axle weights?
A TPMS system is helpful although a tad expensive but then again tires are cheap ... right?

No feedback through steering wheel or speed wobble.
Have not checked front end suspension or steering though steering gearbox has been rebuilt and tie rod ends replaced.
Each wheel has been weighed and front wheels are very close in weight.
I have TPMS, but that doesn't help with tire wear unless pressures are way off.

eagle19952 · March 21, 2015, 08:30:12 PM

i would suggest that it would need to be something that is pertinent to any axle position, i have had a tire scallop on a tag axle.
i do not think it is a steer problem, probably a suspension or shock problem.

belfert · March 22, 2015, 05:13:15 AM

Quote from: eagle19952 on March 21, 2015, 08:30:12 PM
i would suggest that it would need to be something that is pertinent to any axle position, i have had a tire scallop on a tag axle.
i do not think it is a steer problem, probably a suspension or shock problem.

I had forgotten that this also happened on a tag axle tire in the past. I had this happen to one tire on the front axle and one tire on the tag axle. I moved the one good tire on the front to the tag position when I got new tires in the front.

How hard is it to replace shocks? I'm not sure mine have ever been replaced, but the local bus shop thought they were still good when I got the bus.

luvrbus · March 22, 2015, 06:11:07 AM

If the scallops are on both sides of the bus front tires I would say it is worn front end parts like the king pins or A frame bushings that is a independent axle on each side with A frames upper and lower isn't it ? sorta like a Eagle suspension

Lin · March 22, 2015, 04:39:56 PM

Best case would be balancing, but if it's happening on both sides that would seem unlikely. It would seem that you will have to find a good front end shop. They should be able to tell you about any suspension, shock or alignment issues.

belfert · March 22, 2015, 05:22:36 PM

Quote from: Lin on March 22, 2015, 04:39:56 PM
Best case would be balancing, but if it's happening on both sides that would seem unlikely. It would seem that you will have to find a good front end shop. They should be able to tell you about any suspension, shock or alignment issues.

I am pretty sure the tires were balanced. This happened on two sets of tires. The steel wheels were replaced with the current set of tires. I wanted to take pictures today, but I haven't felt that great today so I didn't make it out there.

I have taken the bus to the shop in Elk River, MN that Craig mentioned before for steering work and I plan to take it back there to look at this issue too. I was hoping to get over there in the next week or two, but I remembered that spring road load restrictions are in place and the bus is over the limit for some of the roads.

Jim Eh. · March 22, 2015, 10:54:51 PM

Oh yeah, and how many miles on each of those problem tires?

Seangie · March 23, 2015, 04:18:21 AM

Brian,

I've had the same issue and have been told the same things these guys are saying. Have your kingpins rebuilt (fun! not) and shocks replaced. I need my kingpins rebuilt and just need to schedule a week at some point in tthe future to make it happen.

-Sean