I don't know if this helps (and I just joined so it may be answered elsewhere) but I bought a G8 today. While test driving it, the car shakes. Not a lot but enough. Since I had heard this was an issue, I was extra sensitive to it. When I returned, I asked the dealer what was up. My salesman didn't know but he called someone else over to ask. That person said it is a common problem with the G8s and he wasn't sure why but he would check recalls and what not. Well for me, the deal was off until he came back with a printed page which said certain GM models, G8s included, had received faulty tires. The recommendation was to rotate and balance them (don't know how that helps) and that should correct problem. He said if that didn't, they'd replace the tires. So I bought the car with the intention of turning around and going back if needed. I pick it up tomorrow so I will know soon.