I've read several posts that mention a distinct shudder/vibration during braking. I had the same problem for about six months and finally cured it by installing new (to me) type shims in the rear brakes. The shim is cut out so the brake piston contacts the shim with half it's diameter while contacting the pad backing with the other half. I suppose the result is more pressure on the half of the pad covered by the shim. Anyway, they come from Volvo for about $10.00 a set and they cured my problem.