I have a 2005 grand caravan and just rotated the tires. There has been a bad vibration and I figured that a tire was out of balance. So, I found that the passenger rear tire is chopped really bad and just on the outside portion of the tire. What could be causing this problem. the tires are Firestone Affinity touring? Thanks Matt

 

In my case it was weak rear shocks. I had mistakenly installed shocks for a standard suspension. My van has the touring suspension. Both rear tires were cupped. I rotated the tires and saw it starting again with those tires. Changed the shocks and the cupping stopped progressing. Installed new tires 20K miles later and no cupping 40k miles on.

 

Thanks Cougar41. A friend at work said it sounded like a strut or shock, so I think you just confirmed it. Matt