Our pampered (virtually no city driving, mostly highway ... still on original front and rear brake pads) 1998 E320 with less than 29,000 miles has developed a vibration in the rear when braking at 60 - 70 mph. Today I pulled the rear wheels and noted that there are a series of radial marks on the rear rotors, some 20 marks spread around the braking surface of each rotor. Although it's difficult to see with the backing plate in the way it looks like matching marks are on the backside of the rotor. Are these marks very fine radial cracks, and are they commonplace on MB rear rotors? The part number for the rear rotors is 2104230612 with a minimum thickness of 8.3mm ... the rotors have very little wear.

Some 2 years ago I replaced the rear rotors on my parents' 1995 E320 with 30,000 miles because an independent mechanic mentioned that he noticed a rear vibration when braking at 50 mph. After removing the rear rotors I noticed radial cracks through each rotor and they were also warped. The mechanic suggested that the original owner likely drove with one foot on the brake pedal causing the rotors to overheat and crack. I don't ride the brakes when I drive I so I know that's not the cause of the rotor problem. Also, I only wash our cars when they are cool so I haven't hosed down hot rotors.

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Fred Hoelzle