Could it be possible to have a bad disc rotor that would make this sound(wop wop wop, not loud but definitelly happening on each revolution of the wheel)? My tires have 8K mi, 6mos old and I'm almost sure that it is not the tires(dealer rotated at 7500, says it was the front passenger tire, noise still exists). Looking for opinions/help.<p>Also if ballance needed what type of weights do I ask for(I can just see someone hammering on the cheap ones and tearing up the wheels). Any/all help/suggestions appreciated...<p>98.5 A4QMS2.8 Avant