Non-stress relieved cast iron will warp the first time it gets hot. Cheapo rotors will certainly not be properly made (as is the case with nearly everything from China -- can't wait till GM goes bust from defective engines!!!)

Replace with OEM rotors.

Used pads are OK, I suppose, particularly if they dont' have much milage on them, so long as the face is still flat. If ripply, or groaning or squealing, I'd replace them as well. If they show significant wear, get new ones, they aren't that expensive.

Peter

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1972 220D ?? miles
1988 300E 200,012
1987 300D Turbo killed 9/25/07, 275,000 miles
1985 Volvo 740 GLE Turobodiesel 218,000
1972 280 SE 4.5 165, 000 - It runs!