Cupped tires: finding the cause

'03 C4S with stock suspension (original as far as I know) was in the dealership this week for 60K service and they told me the inner part of rear tires showed significant cupping(noisy(roar) ride also - although quieter the faster you go). Had the stock alignment done in the past 2 months and they had no problems completing it. My question is this: if the reason for the cupping is suspension setup/problem, would this not have shown up during the alignment? Not planning on replacing tires before I put snows on in ~60 days - any risk to waiting(will replace the rears before summers go back on next spring)? Should I have the alignment redone as soon as the snows go on? How do I know when it's time to replace the shocks?

Quotes source post: 11629146

Hate to say this but unless you got a printout of the actual alignment settings the alignment can be anything. Even if the alignment settings are ok there are various differences of opinion as to what settings are the best. Basically the differences are related to the amount of toe in both at the front and the rear. Excessive toe in (or toe out) can result in the tire wear you are observing. Also, if the tires were not new when the alignment was done this can affect the quality of the alignment. Thus the problem is with the worn rear tires even if you have an alignment done the outcome may not be that good. I would also be reluctant to have you align the car with the snow tires as these being different from the summer tires might result in less than optimum alignment for the summer tires. To me it would be of less concern to run winter tires with summer tire alignment settings than run summer tires on winter tire alignment settings. 'course, I'm assuming a given alignment with summer tires would not read the same with winter tires mounted and vice versa. Even if you elect to live with the suspected alignment over the winter you are still faced with come next spring having the alignment redone with the worn rear summer tires back on the car. Winter tires though are softer and this alignment could have them worn out before the season is over with, unless you spend all winter on snow/ice and none on dry pavement. I guess what I would do is have the alignment done now. Be sure you get a before and after printout. Keep in mind even if the alignment is *perfect* the tires will take some running to adapt to the new alignment so the car might not feel as good as it would had the alignment been done with new rear tires. If the rear tires are worn to the wear bars or worn in such a way to render them bad (to the belts) you should replace the rear tires and have the alignment done.

Cupping is not an alignment problem. Worn shocks cause cupping.

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+1 Tires are not making proper contacts with the road surface due to worn suspension parts http://www.procarcare.com/includes/c...dtirewear.html

Tire pressure too.

Quotes source post: 11629414

Not on just the inner edges. Alignment.

It shows up on the inside because that's where the rear tires normally wear out first.

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Only when the alignment is wrong. As I have mentioned before both my Boxster and Turbo get superb rear tire life with the rear tires wearing very evenly across the tread and both cars have a proper alignment without among other things the aggressive toe in some believe is best. I can add there is no harm in having the shocks checked out. (And having the suspension/steering checked for a bent or worn or damaged component.) Sure, the odd shock fails. Not common but the possibility shouldn't be ignored. My info is generally if the shock isn't leaking it is ok. The shocks on my Boxster are not leaking and have 285K miles on them. It is safe to say they are more worn than not, but even so the front tires show no signs of cupping. The only time the tires on either one of my cars exhibited the early signs of cupping was on the front tires of the Turbo which developed some out of spec toe out due to a very low speed, but not low speed enough, encounter with a low sidewalk. The tires set up a howl at speed that had me believing a wheel bearing was bad. But a tech checked the car and spotted the signs of abnormal tire wear. Back home and after an alignment and after some miles the howl went away and the front tires (and rear tires) are wearing evenly across the tread face.

Thanks all. I had a before and after on the last alignment and they had aligned it to a stock setup. The tires were howling before and after that alignment. To make matters works I clipped the rear wheel on a curb and that be making things worse. So I may have to have it checked again. The rears are pretty much done so I was planning on replacing them by the time spring rolls around. No leaking shocks here so I will take it they are OK unless anybody has some other suggestions of figuring if they are worn. The car does not rock if pushed on - pretty tight still at 61K miles.