What causes tag axle tires to scallop?

belfert · October 09, 2011, 04:21:39 PM

My tag axle tires are wearing in a weird pattern. There are spots were it looks like "scallops" like somebody used a large pocket knife to carve out a chunk of the tire. Could this be problem with alignment of the wheels somehow? The two tag wheels are independent of each other. The tires have maybe 30,000 miles on them.

I'm thinking I may need to buy new steer tires next Spring/Summer and move the steer tires to the tag. I should probably take the bus to Precision Frame and have them look at the tire wear.

edroelle · October 09, 2011, 05:00:38 PM

I have seen that problem many times on G159 Goodyears. At a rally, Goodyear claimed they had never seen that. Goodyears are not on my list of replacement tires. Either they lied, or were so ignorant, I will spend $$ with other companies.

After further investigation, I was told that some companies put "equalizer" grooves on the outside diameter. They need strength so they don't get ripped-off. Supposedly, the equalizer grooves prevent/minimize the "scallops".

Ed Roelle
Flint, MI

luvrbus · October 09, 2011, 05:33:00 PM

On your bus with air bags only on the tags I would check the air pressure on the down force Dina's are famous for not having enough down force or weight on the tags ,then if the shocks haven't been replace that is another problem that will cause cupping along with running to low of tire pressure

good luck

belfert · October 09, 2011, 05:40:16 PM

Tires are Firestone FS590 Plus currently running about 85 PSI. It don't know that it is cupping. It is like someone removed chunks of the tire with a pocket knife like whittling.

The air gauge on the tag air bag regulator shows the proper 43 PSI for the air bags. I noticed there is a second pressure regulator under the bus that has a tag that says it is hard set at 43 PSI. What would be a good way to verify the air pressure?

The two rear axles weigh approximately 27,000 lbs. I don't recall what the tax axle alone weighed off the top of my head.

What is a good way to test if the shocks are good? I was told when the brakes and bearings were done that the shocks were good at that time.

buswarrior · October 10, 2011, 10:05:49 PM

With tags, it's bouncing, loose bushing/locating points, or flat spots from sliding a tire under braking.

Put the tag axle on the scales and see what you get for a load. Even better if you can check each one separately. Need a scale with lots of room around it...

For what a pair of shocks cost, if you haven't done them, call it preventive maintenance and rule them out?

happy coaching!
buswarrior

rv_safetyman · October 11, 2011, 04:56:40 PM

Brian, you make it sound like the tires are "chunking" or losing part of the tread. If that is the case, it would almost surely be a defective tire. I can't imagine getting two defective tires.

I suspect the what you are describing is a wear issue, albeit a strange one. Wheel bearing that are adjusted too loose will give strange wear patterns and it doesn't take much (voice of experience).

You could check the pressure by putting a gauge in the air line - can probably put a "T" in at the air inlet to the airbag, or simply unhook the tubing and terminate it with a gauge. if it were me, I would put a permanent gauge in the system and mount it in the driver compartment. You could go one step further and have either a dump valve or regulator in the driver area to help with traction or on sharp turns.

You could also check the axle by running it across scales (many rock quarries will work with you, or you could go to a truck stop and pay to have it weighed). Be sure to weigh each axle.

Jim

belfert · October 11, 2011, 05:44:27 PM

I should take a picture of the wear issues on the tires if I can. I have the exact weights of each wheel somewhere and I haven't added anything since the weights were taken. I'll have to see if Precision Frame still has the weights in their computer.

There is already a pressure gauge at the regulator for the air bags. I just want to verify the pressure. Dina is pretty adamant about running 43 PSI. I'll have to trace the tubing and find a place to put another gauge.

Just Dallas · October 11, 2011, 06:39:21 PM

Brian, it really sounds like wheel hop caused by poor shock absorbers. The only real way to check a shock on a bus is to remove it and see if it has the required push/pull. CAUTION: some shocks only have push and some only have pull, depending on application, see what your mfg requires since if you pull one off, you might as well replace it.

The tech telling you that the shocks look good, was worth exactly what he told you. They weren't leaking fluid and there was no visible damage. Without pulling the shock there really was no other test he could do.

Shocks are under $100/ea... depending on what you want, while your at it change the others too, they are probably all about the same age.

Good luck to you my friend, I hope it works out for ya.

belfert · October 12, 2011, 09:21:03 AM

It looks like I should get new shocks for at least the tag axle and probably just do them all. I'll have to see if there is a part number on the shocks anywhere. I would prefer not to order them from MCI if I can help it.

C&J Bus Repair redid all my brakes and wheel bearings when I bought the bus. I asked about the shocks and JD said they were about the only thing that was still good at that time. I doubt the shocks have ever been replaced knowing the track record of my bus.

luvrbus · October 12, 2011, 10:44:24 AM

Use Gabriel 85-314 for the front then use Gabriel 89425 gas adjustable for the rear and tag set on med to start with if you don't like ride adjust more or less and you can order those shocks through Auto/Zone for 50 bucks ea

good luck

belfert · October 12, 2011, 10:50:53 AM

Quote from: luvrbus on October 12, 2011, 10:44:24 AM
Use Gabriel 85-314 for the front then use Gabriel 89425 gas adjustable for the rear and tag set on med to start with if you don't like ride adjust more or less and you can order those shocks through Auto/Zone for 50 bucks ea

It seems you have recommended these same shocks for Eagles too. Do the Dina and Eagles take the same size shock?

luvrbus · October 12, 2011, 10:56:10 AM

Yes they do and so do most buses, just never use a single action shock on the front they need to be double action shocks you have 6 or 8 shocks I seen Dinas with both setups

good luck

belfert · October 12, 2011, 11:04:58 AM

I checked the Autozone website and called a local store. They don't even have the price on the 85314 and said they would need to order it from the manufacturer. The other they can get no problem. Ryder Fleet Products shows four weeks for the 85314. I don't have a problem waiting a few weeks if necessary.

luvrbus · October 12, 2011, 11:22:42 AM

I buy those shocks from Auto/Zone here all the time the last ones were 51.80 with tax I just checked a invoice,sorry Brian it is the 89425 I buy I do have to wait on the front from Ryder,check Jefferson in OKC he stocks the 85314 have no idea about the price but sometimes he is cheaper on shocks than most places

good luck

Len Silva · October 12, 2011, 12:50:04 PM

http://www.amazon.com/Gabriel-85314-FleetLine-Heavy-Absorber/dp/B004K7XQ2S

http://gabriel.com/our-products/heavy-duty-commercial/heavy-duty-detailed-product-page?partnum=85314

Google the part number, lots of good results.