I went through this on my first quattro, had 5 sets of rotors and pads under warranty, blamed my wheels (BBS), which dial-indicated to less than 10% of runout spec, they eventually replaced the hubs and bearings which cured my problem to run the next set of brakes for 130,000 miles.

If you have a dial-indicator, that would be your next step IMO. If not, try spinning the wheel with something propped close to the wheel and look for lateral and radial runout at the wheel and at the tire.

Often a slow swerve left/right as you're braking will make it better/worse to indicate which side is the offendor.

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Gone to the dark side

- Jeff