I wonder if you can help me. In January I bought an Audi A4 Avant that was a little over three years old and had done some 25,000 miles. Shortly after buying it I noticed a rhythmic thump, fairly slight, that seems to be coming from the left front and to be correlated to the revolutions of the wheels. It is easier to detect at lower speeds; at higher speeds it blends into a constant slight whine. A garage checked it and diagnosed a deformed or distorted tyre. However a tyre place removed all four wheels, spun them, could not detect any distortions and pronounced the tyres OK. The wheels are 17-inch diameter. Any thoughts?