I go for James's theory...balence problem. If there was some sort of ring it would certainly throw off the balance because the rim was balenced off the car and when the lug nuts were put back on, it would throw off the work that was just done. Just put on new tires on the wife's car and asked that the weights be put on the inside only...that's the way they were when I took the car in. Above 55 the steering wheel shook. Took it back and told them to try again...still shaking. Now, either I take it someplace else and pay to try and have it corrected or tell the first place to put weights on both sides.
