The grove is more than likly the wear of someone using extreme metalic pads or an aftermarket brand of lifetime warranty pads,, really hard surface on them,, Replace the rotor as the tolerances on Volvo rotors are very slim.. Get a good brand rotor and not some junk if you want them to last,,also the parking brake is inside the rotor,, there are two brake shoes, not pads, that need to be replaced if rusted, they seldom wear out as all they do is hold the car in place. You can get them from the local parts store if they can order them, cheaper that way..Get a Bentley manual and read it,, it will give you all the information on the procedure..Bentley can be ordered on line or from the local bookstore,, well worth the cost of around $40.00.......Good Luck.:)Max
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Max..1989 244 DL 5 Spd., Bilstein HD, Turbo Swaybars, Poly Bushings all round, Turbo Wheels, Black leather interior, Electric mirrors, LED dash and gauge lights.