Two sets of rotors and no improvement greatly reduces the chances that it is the rotors.

Agree with the wire brush on the hub and rotor mating surface, as well as where the wheel sits on the hub, to ensure they are seated properly. We aren't talking about the friction surface, but rather the mounting surface.

It isn't likely a brake problem (pads, caliper, or rotor) but rather something not balanced rotationally (ie not seated properly, or dynamically unbalanced), or something loose in the suspension (mentioned by others) that braking sets off. If it wasn't there before the brake job, I would be looking for the former.

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2007 X3 3.0si, 6 MT, Premium, White

Retired:
2008 535i, 6 MT, M Sport, Premium, Space Grey
2003 X5 3.0 Steptronic, Premium, Titanium Silver
2002 325xi 5 MT, Steel Grey
2004 Z4 3.0 Premium, Sport, SMG, Maldives Blue