Yup, the rear wheels are on bushings at their suspension pivots. These wear and can need replacing or adjusting.
I don't know how 'much' they can be adjusted before you need new parts.
Cupping means a balance or dead shock issue usually to me though, peeling off an inside or outside edge suggests alignment.... Could be wrong.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's - Gone to the rust pile... Canadian Off Road Trips Photos: Non members can still view! Jan/06
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Most places offer a 4 wheel alignment these days, you will have to phone around for pricing.
Are the tires dead now? If cupped or worn bad enough, they won't line up properly so you will need a fresh set. If they are a write off, then holding off on the fix for a while isn't going to cost much more likely.
I would also try a different shop than gave you the bad news because I don't agree with their diagnosis. I think you will get the alignment and 'then' be told 'oh, the shocks are dead too' by the way or 'the balance is way off now' too...
I blew/wore out the rear swing arm bushings on on rally car I used to own. These were worn enough the whole wheel would swing in and out if you jacked up the side and the tires did 'not' cup in any way, they peeled the edges.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's - Gone to the rust pile... Canadian Off Road Trips Photos: Non members can still view! Jan/06
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Do it every 5k miles (or at every oil change). Independent rear suspensions on light FWD cars will often cause diagonal wear on tires, which will spiral out of control if they are left in the same positions for too long. Just the uneven wear of front to rear tires is reason enough to rotate regularly. Add both reasons and you are throwing tire $$$ away by not rotating properly.
Toe is adjustable in the rear of your car, so do consider doing the 4 wheel alignment after you get new tires. Rear toe out of spec just compounds the wear phenomenon mentioned above.
When you say 'cupping' on tires, that means scallop shaped wear marks are happening in a pattern around the tire.
This implies a harmonic wobble in the rubber. This can be caused by a tire that is out of balance or a bad shock absorber allowing a slightly out of balance tire set up a vibration. A poor alignment can likely make this worse, but when I think alignment troubles, I think of the inside or outside edge of the tire showing unusual 'even' wear.
A test for shocks you can do yourself is to bounce each corner of the vehicle as hard as you can and let go. You then count the bounces to stop. A good shock will stop bouncing at 2 bounces or less. If it hits three bounces after you let go, the shock is done for.
You can also jack up each side and see if the wheel physically moves in or out.
Loose rear wheel bearings can also allow a harmonic to set up cupping the tires. Again if you jack it up and they are loose, the wheel will wobble
I could be wrong here, but rear wheel alignment is the last thing that comes to mind for cupping.
Mike
86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00
88 Cherokee 235 BFG AT's - Gone to the rust pile... Canadian Off Road Trips Photos: Non members can still view! Jan/06
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(More Off Road album links at bottom of the view page)
Rear wheel alingment is as important as front. The cupping that the shop reffered to could be the diagional ear marks in the tread face caused by the toe being out of spec. The Ford Escort and Tempo often exhibited the diagional wear and if the toe was out enough would rear end steer causing problems on slippery roads
I echo what everybody has said about the rear alignment.. It can be very important. Stepdaughter had two tires worn to the steel belts and it occurred quickly after she rotated tires, so she bought two new and had the front end aligned. This didnt make sense with the rotation she had done so I asked her to go back and have them check the rear alignment (Buick Regal).. It had a bent suspension member and the alignment was dangerously off.
On my van, I had cupping on the front tires (high buck Michelins), so went back to the tire supplier. I had no suspension problems, nor out of alignment conditions. They (Discount Tire) told me I had not rotated quickly enough and this sort of cupping was not unusual. They rotated the cupped ones to the back, and the noise and wear problem was brought into reasonable limits. Unfortunately, they used torque stix on their impact wrenches, and warped a set of rotors for me.
That was a couple of years ago, and I now have some 62,000 miles on those Michelins. I rotated them myself the last time, since the local tire merchant (NOT Discount Tire) never heard of a torque wrench.
Well I've REALLY learned something here. Thanks so much guys!!
Just had no idea that rear wheel could get out of alignment. But its also my fault that when getting new tires, I haven't been getting ANY kind of alignment done.
I bought these tires at Costco where they have lifetime rotation as well.
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