I have a 1999 Nissan Altima with about 120K miles. It still runs great and I just got new tires. The day after they were installed, I took it on the interstate and it shook terribly when I drove 60 miles an hour. When I took it back to the mechanic who installed my tires, he said that they no longer do a "high speed" balance and that there is only one true balance for a car. He said the problem was caused by rims being warped in the front right tire. He also said that the new tires/new tread are causing some of the initial problem and as the tread wears the problem will get better. I don't know much about cars but this didn't seem look a proper explanation to me. Any advice would be appreciated. Thanks!