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Front Brake Rotor Replacement
 
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Pelican Technical Article:

Front Brake Rotor Replacement

Steve Vernon

Time:

3 hours3 hrs

Tab:

$40

Talent:

**

Tools:

12mm, 18mm socket, T30 Torx driver flathead screw driver

Applicable Models:

Mercedes-Benz W203 (2001-07)

Parts Required:

New rotors

Hot Tip:

Pre-soak rusted bolts in penetrant oil

Performance Gain:

Car stops better

Complementary Modification:

Replace Pads

Replacing your brake rotors is a very easy job to perform on your Mercedes and a great way to get started on "Doing it yourself". In general, you should inspect your brake pads and rotors about every 25,000 miles, and replace them if the material lining of the pad is worn down enough to trigger the pad replacement sensor or there is less than a quarter inch of material on the pad. In reality, most people don't inspect their pads very often, and usually wait until they see the little brake-warning lamp appear on the dashboard. It's a wise idea to replace the pads, and inspect your discs as soon as you see that warning lamp go on.

If you ignore the warning lamp, you may indeed get to the point of metal on metal contact, where the metal backing of the pads are contacting the brake discs. Using the brakes during this condition will not only give you inadequate braking, but will also begin to wear grooves in your brake discs. Once the discs are grooved, they are damaged, and there is often no way to repair them. Resurfacing will sometimes work, but often the groove cut will be deeper than is allowed by OEM specifications. If your pads are grabbing or pulsing when you come to a stop, there is a very good chance your rotors are warped and in need of replacement as well. NOTE: If your rotors are really grooved you should replace your brake pads as well.

The first step is to jack up the car and remove the road wheel. This will expose the brake caliper that presses the pads against the disc.

To replace the front rotors on the Mercedes W203, you need to remove the caliper.

Begin by unplugging the wear sensor attached to the pad. It simply pulls out from where it is attached to the caliper.

Use a large screw driver between the pad and disk to compress the caliper piston back into the caliper. This will make removing the caliper from the disk easier, especially if the risks are worn.

Next remove the two 12mm bolts holding the caliper to its mount.

After the guide bolts have been removed, you should be able to simply lift the caliper off of its mount. Suspend the caliper using some zip-ties or rope until you are ready to work with it again. Never let the caliper hang from its rubber hose (this can damage the brake line)

Once you have the caliper removed, inspect the inside of it. Make sure that the dust boots and the clamping rings inside the caliper are not ripped or damaged. If they are, then the caliper may need to be rebuilt. At this point, you should inspect the brake discs carefully. Using a micrometer, take a measurement of the disc thickness. If the disc is worn beyond its specifications, then it's time to replace it along with the one on the other side

If your rotors are really worn you may need to take a C-clamp and old brake pad to push the caliper piston back into the caliper. This is because the new rotors are going to be quite a bit thicker than the old worn-out ones, and the piston is set in the old rotors position. Push back the piston using the clamp, being careful not to use too much force. Using a screwdriver here can accidentally damage the dust boot and seals inside the caliper, and is not recommended.

Be aware that as you push back the pistons in the calipers, you will cause the level of the brake reservoir to rise. Make sure that you don't have too much fluid in your reservoir. If the level is high, you may have to siphon out a bit from the reservoir to prevent it from overflowing.

Move to the caliper mount bracket and remove the two brake pads from their mounts.

Turn the wheel to give you more room to work. The two caliper mounting bracket bolts are on the inside and if you can give yourself a little more room when doing each side it will help. Remove the two 18mm bolts holding the mount to the steering knuckle. Remove the bracket from the knuckle and set aside.

The next step is to remove the rotor. It is held in place by a T-30 Torx screw. Remove the screw and the rotor will come off the hub. The rotors can get corroded onto the hub and sometimes you need to give them a hit with a mallet to free them up. Anything except the lightest corrosion on the hub face must be cleaned with scotch brite and/or 80 grit sanding discs to keep the mating surface true.

Install the new rotor taking care to line it up with the locating pin and secure it with a new screw or put some Blue Loctite on the old one.

Apply some anti squeal to the back of the pads and install them in there brackets on the caliper mount. With the piston compressed into the caliper reinstall the caliper over the pads and back onto the bracket. Install the guide bolts and torque to spec. Once the caliper is mounted to the bracket, plug the sensor back into the harness.

When finished with both sides, press on the brake pedal repeatedly to make sure that the pads and the pistons seat properly. Also make sure that you top off the master cylinder brake fluid reservoir if necessary. If you have replaced your pads typically takes between 100 and 200 miles to completely break in. Make sure that you avoid any heavy braking or emergency maneuvers during this period.

The first step is to jack up the car and remove the road wheel.
Figure 1

The first step is to jack up the car and remove the road wheel. This will expose the brake caliper (red arrow) that presses the pads against the disc (yellow arrow) .

Begin by unplugging the wear sensor attached to the pad.
Figure 2

Begin by unplugging the wear sensor attached to the pad. It simply pulls out from where it is attached to the caliper (yellow arrow) .

Use a large screw driver between the pad and disk (yellow arrow) to compress the caliper piston back into the caliper.
Figure 3

Use a large screw driver between the pad and disk (yellow arrow) to compress the caliper piston back into the caliper. This will make removing the caliper from the disk easier, especially if the risks are worn.

Next remove the two 12mm guide bolts (yellow arrows) holding the caliper to its mount.
Figure 4

Next remove the two 12mm guide bolts (yellow arrows) holding the caliper to its mount.

After the guide bolts have been removed, you should be able to simply lift the caliper off of its mount.
Figure 5

After the guide bolts have been removed, you should be able to simply lift the caliper off of its mount.

Suspend the caliper using some zip-ties or rope (yellow arrow) until you are ready to work with it again.
Figure 6

Suspend the caliper using some zip-ties or rope (yellow arrow) until you are ready to work with it again. Never let the caliper hang from its rubber hose (this can damage the brake line).Once you have the caliper removed, inspect the inside of it. Make sure that the dust boots and the clamping rings inside the caliper (red arrow) are not ripped or damaged. If they are, then the caliper may need to be rebuilt.

To install the new brake pads, you will need to take a C-clamp and old brake pad (yellow arrow) to push the caliper piston back into the caliper.
Figure 7

To install the new brake pads, you will need to take a C-clamp and old brake pad (yellow arrow) to push the caliper piston back into the caliper. This is because the new pads are going to be quite a bit thicker than the old worn-out ones, and the piston is set in the old pad's position. Push back the piston using the clamp, being careful not to use too much force.

Be aware that as you push back the pistons in the calipers, you will cause the level of the brake reservoir to rise.
Figure 8

Be aware that as you push back the pistons in the calipers, you will cause the level of the brake reservoir to rise. Make sure that you don't have too much fluid in your reservoir. If the level is high, you may have to siphon out a bit from the reservoir to prevent it from overflowing.

Move to the caliper mounting bracket and remove the two brake pads from their mounts (yellow arrows).
Figure 9

Move to the caliper mounting bracket and remove the two brake pads from their mounts (yellow arrows).

Turn the wheel to give you more room to work.
Figure 10

Turn the wheel to give you more room to work. The two caliper mounting bracket bolts are on the inside and if you can give yourself a little more room when doing each side it will help. Remove the two 18mm bolts (red arrows) holding the mount to the steering knuckle. Remove the bracket from the knuckle and set aside.

The next step is to remove the rotor.
Figure 11

The next step is to remove the rotor. It is held in place by a T-30 Torx screw (red arrow). Remove the screw and the rotor will come off the hub. The rotors can get corroded onto the hub and sometimes you need to give them a hit with a mallet to free them up.

Anything except the lightest corrosion on the hub face (red arrow) must be cleaned with scotch brite and/or 80 grit sanding discs to keep the mating surface true.
Figure 12

Anything except the lightest corrosion on the hub face (red arrow) must be cleaned with scotch brite and/or 80 grit sanding discs to keep the mating surface true.

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Comments and Suggestions:
Kodi Comments: I don't believe the bolts holding the caliper to the hub are 12mm on the rear. The images provided here are also for the front, not the rear. I need to find where I can buy the rear caliper mounting bolts.
May 14, 2016
  Followup from the Pelican Staff: I will check with the author and have the article updated if needed. - Nick at Pelican Parts  
Frank Comments: What a great site. I have replaced a number of pad sets over the years....but not on an MB Suv. It was nice to get the assurance that it held no mysteries. Thank you for your assistance
February 2, 2015
  Followup from the Pelican Staff: Thanks for the feedback. Glad we could help.
- Nick at Pelican Parts
 
pasha Comments: So if I have 25mm rotors that means I can only have 3mm of wear before replacement?
August 30, 2014
  Followup from the Pelican Staff: Correct. - Nick at Pelican Parts  
pasha Comments: Nick, can you tell me the minimum thickness for the front pads on a 2007 C230 sport. After 20k miles I have a slight lip on the rotors and not sure if they should be peplaced or not? Thanks very much
Roger
August 23, 2014
  Followup from the Pelican Staff: There are a lot of options for your vehicle. The wear limit is either 22mm or 26mm, depending on if you have 25mm or 28mm rotors when new. - Nick at Pelican Parts  
Robert Comments: Suggest you add the torque specs for the caliper mounting bracket, the caliper, and the locating screw. Would be helpful in finishing the job. You did that on another version of this for E class. I suspect they're the same but don't know for sure.
April 13, 2014
  Followup from the Pelican Staff: Thanks for the feedback. We don't have all of the specs. We suggest grabbing a repair manual, torque specs, special tools will be listed.
- Nick at Pelican Parts
 
Finesherb Comments: I seem to get a lot of dust after changing the brake pads. Is there a brand or type you would recommend?
February 27, 2014
  Followup from the Pelican Staff: Ceramic brakes create minimal dust. Give our parts specialists a call at 1-888-280-7799. They can help you find the right part.
- Nick at Pelican Parts
 
Carlosfe Comments: Do this same steps apply to the rear rotors as well or is there a different set of steps? I have a 2003 SLK 320.
December 12, 2013
  Followup from the Pelican Staff: The rears are a bit different due to the mounting points of the caliper. But you can use this a rough guide. - Nick at Pelican Parts  
shorty Comments: what is the name of this disc??
October 22, 2013
  Followup from the Pelican Staff: The brake rotor. - Nick at Pelican Parts  
vanehrdz Comments: how can i find these discs???
October 21, 2013
  Followup from the Pelican Staff: Give our parts specialists a call at 1-888-280-7799. They can help you find the right part. - Nick at Pelican Parts  

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