8 months ago I replaced the rotors and pads on my S550. I did the break in procedure, up to 55 and fast decel to 10 and did that 5 times.. Squeak Sqawk it was awful.. I bought aftermarket rotors and ceramic pads. Rotors were xdrilled and grooved..I just ordered new rotors and pads.. I will install them this week and hope that fixes it..