There have recently been intermittent vibrations while driving my car. An independent tire shop inspected it and said that one front tire and one rear tire were out-of-round due to tread separation or belt slipping. I suspected this was related to the vibrations I noticed soon after purchasing it used. Two years ago it had Continental dws tires installed, from a Volvo dealer. At the time I assumed it was an imbalance or poor wheel mounting. The dealer inspected it and found uneven camber wear and cupping. He told me there was no tread separation and my car’s suspension checked out, as did the alignment. The intermittent vibration can not be explained by the camber wear and cupping since they are permanent. The independent shop had said that the tire has an internal defect that is allowing shifting in the belts. I truly feel that these tires have a dangerous manufacturing defect. What can I do to get rid of the vibrations?
Replace the tires. It used to be possible to "true up" a tire that was out-of-round by putting the wheel/tire on a special machine that literally ground rubber off of the "high" side of the tire, making it physically round. Volvo delivered these cars from the factory with excessive negative camber settings on the rear suspension that caused the cupping you mention. There is a Volvo Service Bulletins provided to dealers to address this issue: Uneven Rear Tire Wear, Correction of Excessive Negative Camber in Retailer Technical Journal RTJ15309-2009-12-16. The RTJ calls for the replacement of the rear upper control arms with part number 31201356 which reduces the camber by ~ 0.7 deg. It is applicable to 2007-2010 C30 models. I believe the replacement only applies to cars under warranty, but the same control arms should be available for installation, then re-alignment. This should get rid of future cupping of rear tires.
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