I am having the same problem with brake shudder - it usually happens only after the car has been driven a while and the brakes are heated up. It happened a few years back and my independent shop said it was warped rear rotors and replaced pads and rotors. It went a way for a time but is now doing it again. I'm taking it in to another independent shop (Volvo specialty) tomorrow. They looked at it once and said it can be solved only by replacing the rotors. They said if the whole car shudders (which mine does) then it is usually the rear, if the shudder comes thru the steering wheel, then it is usually the front.

But, can my rear rotors be warped already if they only have 15-20K miles on them? I know there has been some discussion on the board that irregularly torqued lug nuts can cause rotors to warp. So far I have not gotten the diagnosis of a sticking brake caliper.

Could there be a "hot" spot on the rotor? Any other thoughts from people who have had this problem? - it seems to be somewhat common. I will update with a new message after tomorrow when the shop comes up with it's take on the problem.

Steve ('94 850, 104K)