Just turned 2k miles, and I am picking up wheel balance problems (rear). I took it to the dealership today and they checked the Balance, they said the balance was out just a little, but not enough to cause the problem, re-balanced them anyway, now these tires have 2k miles on them, They are Goodyear Wrangler SR-A's, now here comes the good part, they said what the problem is, is that the side walls on the tires have hard spots in them causing the problem. I have never heard of it, but they ordered 4 new tires from GM, If anyone else is running into the problem with the 2011's with 20" wheels and Goodyear Wrangler SRA's it may be the same problem. It did not start doing this until about 1700 miles.