Dale, first time I've heard the theory of replacing brake pads on front & rears at the same time. Makes no sense to me.

Once rotors are warped they are warped. They are not going to get better as time passes. Recommend buying new rotors from a MB dealer rather than buying them online. Aftermarket rotors can be warped right out of the box ... good idea to perform a runout check on them during installation. Best to use a torque wrench to tighten lug bolts, if not you may get rotor warping.

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Fred Hoelzle