Wrong brake discs
Having concerns about a noise from the front of his 2006 Audi A4 TDI, the owner brought the vehicle to us. With the vehicle jacked up and the front wheels removed, we were concerned about the amount of brake pad material left and started to investigate a little further. We discovered that the surface area of the brake pads was larger than the area of contact with the brake discs.
Our first thought was that, when the brake pads had last been replaced, the wrong pads had been fitted. Further investigation proved this was not the case and the brake pads were the correct ones for the vehicle. What was wrong was that the brake discs, which were slightly smaller than those that should have been fitted, had allowed the pads to wear on the braking surface, leaving a portion of the pad unworn and overlapping the edge of the disc. This unworn area of pad had eventually come into contact with the inner area of the disc and was making a noise.
New discs and pads not only rectified the problem, but restored full braking power.