My B6 A4 Quattro has recently started to vibrate at speeds over 35mph. It can be felt through the seat base and a small bit through the steering wheel. The sensation is as i would expect if the tyres are flat spotted which causes mini vibrations that can be felt through the car. I initially thought that the wheels needed re-balancing but after doing this it hasnt made any difference. I suspected warped discs but there is no brake shudder when the pedal is depressed. I am not sure if this is specific to quattro cars or whether anyone has epxerienced something similar. Any suggestions would be welcome.