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Mercedes W123 Brake Disc, Rear Replacement

What you need

  1. Mercedes W123 Brake Disc, Rear Replacement, Remove the caliper: adım 1, 1 resimden 1.
    • You will first need to remove your wheel to complete the remainder of this job.

    • Then unbolt the two 19mm bolts on the back of the caliper. They are in very tightly and held in by thread locker, you may need a long wrench or breaker bar to remove these.

    • Lift the caliper off of the rotor and hang it with a wire hanger from the sway bar or other strong point on the car. Do not let the caliper hang by the brake hose, this can damage the hose leading to an unsafe driving condition.

    • Or, optionally, remove the caliper from the car for cleaning and new pad install. See the caliper replacement and break pad replacement guides.

    • The rear rotor can then be simply pulled off. If it seems to be stuck to the rear hub, tap around the outside of the rotor with the wooden handle of a hammer, or a rubber mallet, to break it loose.

    I read this guide in preparation for replacing rear calipers, rotors, and brake pads on my father’s car and found the guide very helpful - thank you! In my case, the rotors were seriously stuck. Tapping around the outside of the rotors seemed to have no effect. Spraying something similar to PB Blaster had no effect. What did work was using a ball peen hammer to hit the rotor hat HARD in several places around the perimeter of the hat - just out from the lug bolt holes.

    Shea Evans - Yanıt

  2. Mercedes W123 Brake Disc, Rear Replacement, Inspect the rear hubs: adım 2, 1 resimden 1.
    • With the rotor off the rear hub is exposed. It may be quite rusty like this. If the rotor was seized to the hub it was because of this rust.

  3. Mercedes W123 Brake Disc, Rear Replacement, Clean the hub surface: adım 3, 3 resimden 1. Mercedes W123 Brake Disc, Rear Replacement, Clean the hub surface: adım 3, 3 resimden 2. Mercedes W123 Brake Disc, Rear Replacement, Clean the hub surface: adım 3, 3 resimden 3.
    • Use a fine grit sandpaper, and optionally a power sander, to work around the flat surface of the hub to remove rust.

    • Then use the sandpaper to remove rust from the raised portion at the center of the hub.

    • The area around the lug bolt holes is recessed slightly and does not contact the rotors so it does not to be fully de-rusted.

    • Spray the hub down with brake cleaner to remove the dust.

  4. Mercedes W123 Brake Disc, Rear Replacement, Protect the hubs surface: adım 4, 1 resimden 1.
    • Now apply a light coat of anti-seize to the surfaces on the hub that contact the rotor.

    • This will help prevent the new rotor from seizing to the surface of the hub the next time you need to remove it.

    • Do not get anti-seize in to the lug bolt holes! This could lead to the lug bolts backing out while you are driving, allowing the wheel to fall off.

  5. Mercedes W123 Brake Disc, Rear Replacement, Install new rotors: adım 5, 1 resimden 1.
    • Now set the new rotor in place. There is a small raised pin on the hub that the rotor has a corresponding hole for. This ensure the rotor is installed correctly aligned with the bolt holes.

    • Spray both sides of the new rotor down with brake cleaner to remove any oils from the factory or from your gloves.

  6. Mercedes W123 Brake Disc, Rear Replacement, Re-install the caliper: adım 6, 3 resimden 1. Mercedes W123 Brake Disc, Rear Replacement, Re-install the caliper: adım 6, 3 resimden 2. Mercedes W123 Brake Disc, Rear Replacement, Re-install the caliper: adım 6, 3 resimden 3.
    • Now re-install the caliper. Make sure to put blue thread locker on the caliper bolts.

    • Torque the caliper bolts down to 115 nm / 85 lb-ft

    Just a note regarding replacing the calipers…I installed new calipers. To connect the brake line to the calipers, I had to screw the calipers onto the brake line. (Literally, holding the end of the line still and rotating the calipers. ) Then, after bolting the calipers on, I used a wrench to do a “final” tightening on the brake line nut.

    Shea Evans - Yanıt


When you are finished be sure to go on a test drive before going on any long trips.

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Nicolas Siemsen

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This is a great, well illustrated guide. I just want to add that the parking brake shoes need inspection and may need adjusting.

After step six, the star wheel can be rotated with a flat blade screwdriver. Access is through one of the lug bolt holes if rotated to about 10 o'clock position on the driver side (and about the 2 o'clock position on the passenger side). Just rotate the star wheel until the shoes are tight enough to prevent the rotor/drum from rotating and then back off about 3 clicks.

There are also cable adjustments in board from the drivers side brake to equalize the tension on the two drums and to give the proper amount of travel when the parking brake petal is pressed.

SJM - Yanıt

Thanks! Good advice. I did inspect mine while the rear disc was off. They need replacement. I didn't have the parts on hand. I bought the parts and will be replacing them in a few months. When I do I'll write a guide on that job, and also a guide on adjusting them. I'll then link them from this guide. In the mean time your comment will hopefully help a few folks!

Nicolas Siemsen -

7.17.2016 ~ I don't see any how to for the park brake shoes.....-Nate

vwnate1 - Yanıt

True! I haven't had to do this on my cars so have not written a guide yet. You are more than welcome to write one, if you have the desire!

Nicolas Siemsen -

Love the explanation how to take the disc off, tap it off, and then you show a picture (step 2) of a parking brake shoe minus its friction material. If there is a lot of resistance, the possibility is a lip has formed on the drum part, so backing off the adjuster for the parking brake is needed to remove the rear disc/drum. Otherwise get ready to buy a couple of new parking brake shoes (so as not to be a parking “break”).

Alan - Yanıt

Look closely at Step 2 photo. The friction material is missing on one brake shoe and lifting on the other. If the disc/drum is hard to remove, it is likely there is a lip on the drum edge that is catching on the brake shoes. Bashing the disc off will likely damage the friction material on the shoes. It would be better to back off the shoes by turning the star adjuster with a flat blade screw driver poked through the wheel bolt hole. Just remember to adjust tight enough so the wheel locks, then back off a couple of clicks, after putting on the new disc/drum.

Alan - Yanıt

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