Yesterday, I rotated the tires myself by lifting one wheel at a time and using the spare wheel.

Because my W124 is rear wheel drive car, I expected that the front wheels spin as freely as bicycle wheels when lifted.

However, the wheels stop soon after I let them.

I also removed the wheel, grabbed the brake rotor, and spun it. The rotor stopped the moment I let it.

Is this normal?


I went to local Midas shop, and they said that was normal. Instead, they pointed out that my rear rotors were grooved.

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1992 300D 2.5 turbo diesel. 319 k miles.
124.128 chassis, 602.962 engine, 722.418 tranny.

Regarding grooved rear rotors--so what?

Disc brake pads drag. The only thing that retracts a disc brake actuating piston is the flex in the rubber ring through which it passes.

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Kent Christensen
Albuquerque
'07 GL320CDI, '10 CL550. '01 Porsche Boxster
Two BMW motorcycles

Was the car in Park?

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2004 Chrysler Crossfire

rear rotors: they said the calipers were OK, but suggested replacing rear rotors and pads. I declined.

The car was parked when I did the spin test - only one wheel lifted -. Tranny in P, parking brake engaged. But front wheels are independent of the tranny or parking brake.

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1992 300D 2.5 turbo diesel. 319 k miles.
124.128 chassis, 602.962 engine, 722.418 tranny.

The disc brake system is set up so that the pads are in constant contact with the rotors, whether or not the brakes are applied. It improves responsiveness when the brake pedal is applied. I don't know if there is an appropriate amount of drag on the wheel, although I've noticed that on my car it seems to vary from wheel to wheel and from day to day.

I would just make sure the car doesn't pull while coasting, or that the caliper isn't sticking.

Not even close. Too much drag to keep spinning like a bicycle wheel.

Entirely.

North American shops have a fixation with keeping grooves out of rotors. MB rotors are not meant to be machined every time the brake pads are changed. Grooves are normal. Just make sure that the grooves aren't caused by debris or the backing plate of the pad and you'll be fine.

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'94 W124.036 249/040 leder; 8.25x17 EvoIIs
'93 W124.036 199/040 leder; 8.25x17 EvoIIs, up in flames...LITERALLY!
'93 W124.036 481/040 leder; euro delivery; 8.25x17 EvoIIs
'88 R107.048 441/409 leder; Euro lights
'87 W201.034 199/040 leder; Euro lights; EvoII brakes; 8x16 EvoIs - soon: 500E rear brakes
'70 R113.044 050/526; factory alloys; Euro lights

Better stated: They have a fixation on selling service you don't need.

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Kent Christensen
Albuquerque
'07 GL320CDI, '10 CL550. '01 Porsche Boxster
Two BMW motorcycles

It's not that the shops are only trying to sell more work. Some of this 'fixation' is defined by state law that dictates that a 'brake job' must include this work. Rotors and pads no thinner than manufacturer's specifications, no grooves on rotors, etc. The shop assumes certain risks if the job is not done as required.

Of course you, as a DIY'er, can do anything you want at your own risk.