Mercedes-Benz Parts Catalog Mercedes-Benz Accessories Catalog Mercedes-Benz Technical Articles Mercedes-Benz Tech Forums
 
Follow Pelican Parts on Facebook Follow Pelican Parts on Twitter Follow Pelican Parts on Instagram Follow Pelican Parts on YouTube Follow Pelican Parts on Pinterest Follow Pelican Parts on Tumblr
  Search our site:    
View Recent Cars  |   Cart  | Project List | Order Status | Help    
 >  >
Rear Brake Rotor and Caliper Replacement
 
Bookmark and Share

Pelican Technical Article:

Rear Brake Rotor and Caliper Replacement

Tom Morr

Time:

5 hours5 hrs

Tab:

$25 to $65

Talent:

***

Tools:

Floor jack, jack stands, wheel chocks, wood blocks, hammers, punch, flat head screwdriver, ratchet, 16mm socket, C-clamps or piston-retraction tool, brush

Applicable Models:

Mercedes-Benz R170 (1998-04)

Parts Required:

New rotors, calipers, penetrating spray, brake cleaner

Hot Tip:

Inspect and adjust the parking brake while it's accessible

Performance Gain:

Car stops better

Complementary Modification:

New brake pads, wear sensors (if applicable), hoses, parking brake shoes

Replacing R170 SLKs' rear disc brakes doesn't take any special skills or tools other than metric flare wrenches. These disc systems are noticeably easier to service than rear drum brakes. Plus, rotors trap less grime and debris than drums and are somewhat self-cleaning in inclement weather. They're all-around better than drums.

The general procedures shown here apply for both OEM component replacement and also for upgrades such as swapping on drilled/slotted rotors and/or high-performance calipers. Some Mercedes-Benz owners like to make a fashion statement by painting their calipers and if you are so inclined this would be a good time, as you will already have the calipers of the disks

You will need to safely raise and support the car, please see our separate article foe help.

Remove the rear wheels. Once the wheel is off, the caliper's pad-retaining pins can be driven out with a hammer and punch. Then the pads can be plucked out with a flat head screwdriver.

The calipers are mounted with two bolts (16mm heads in the case of the dual-piston/fixed model). Some models have single-use-only self-locking caliper bolts. These need to be replaced for reinstallation.

Once the caliper is off, pinch the hose with a G-clamp or with vise grips protected by a rag, taking care to not gouge the hose. Then break the hose loose with a 14mm flare wrench. Support the caliper so that it isn't dangling by the hose. Then spin the caliper free from the hose, which can remain secured to the steel brake line if the hose isn't being replaced. If retaining the existing hose, put a cap over the exposed threads to keep dirt out.

The rotor is held in place by a retaining screw that takes a 4mm Allen-head/hex wrench or bit. Torque spec is 10 Nm (7 ft-lb/89 in-lb), so it should come loose by hand. Our project SLK's retaining screw was stuck, so we tapped an L-style Allen wrench with a hammer to break it loose.

Theoretically, the rotor lifts off at this point. I reality, it can be corroded in place. First, make sure that the emergency brake is off. Then tap the rotor's hat with a mallet. If it still won't budge, the emergency brake adjuster might need to be backed off (please see our article on adjusting your parking brake). Or, if you're replacing the rotor anyway, tap it with the mallet from the inboard side until it breaks loose.

Make sure you clean the axle flange well to give you a good flat and flush seating of the new disk. Replacement is the reverse of disassembly. Future disassembly is expedited by coating the axle shaft flange's snout with anti-seize before installing the new rotor. Also, adding anti-seize to the rotor's retaining screw will help it come out easier the next time.

Some tips are; Douse all fasteners with penetrating spray as far in advance as is feasible. An abnormally hot wheel signals a possible caliper problem. The hose could be degrading and causing the pistons to stick by blocking fluid flow back to the master cylinder. Leaky calipers need to be rebuilt or replaced. Mercedes-Benz rotors aren't designed to be "turned"/resurfaced on a brake lathe. If possible, measure rotor thickness at the center of the friction area. Minimum-allowable thickness is often cast into the rotor. For R170 rear rotors, 9mm (0.345 inch) is the limit. Visibly warped rotors should be replaced, as should ones that have gray or blue discolorations on their pad-contact area.

Hairline cracks: The rotor should definitely be replaced if the crack is deeper than .5mm or longer than 25mm. Use brake cleaner to remove crud and pad dust from the axle shaft flange and backing plate. Place a pan underneath to catch the debris. A Scotchbrite pad can be used to further clean the axle shaft flange's surface. Brake cleaner and a Scotchbrite pad can be used to clean greasy fingerprints and any other residue off the rotor's friction area once it's installed.

If you replaced the caliper or opened a brake line during this process you MUST bleed the brake system. Do NOT attempt to drive the vehicle before properly bleeding the brake system. Please see our article on how to bleed your brakes.

The brake pads normally pull out easily once their retaining pins and clips are removed.
Figure 1

The brake pads normally pull out easily once their retaining pins and clips are removed.

Two bolts hold the calipers on.
Figure 2

Two bolts hold the calipers on. The R170's have 16mm heads. Some models use self-locking bolts, which are single use only ad must be replaced. Torque spec for installation is 55 Nm (40 ft-lb); using thread-locking compound will help keep the caliper from vibrating loose.

If retaining the brake hose, pinch it shut to discourage leakage.
Figure 3

If retaining the brake hose, pinch it shut to discourage leakage. With the caliper's weight supported by something other than the hose, loosen the line with a 14mm flare wrench. The caliper can be spun off the hose, taking care not to twist or stretch the hose.

The freed caliper can now be rebuilt, replaced and/or painted.
Figure 4

The freed caliper can now be rebuilt, replaced and/or painted. The caliper and hose should be capped to keep dirt out.

Rotor thickness should be measured as close to the center of the pad-contact area as possible.
Figure 5

Rotor thickness should be measured as close to the center of the pad-contact area as possible. Minimum allowable thickness for this rotor is 9mm.

An Allen-head/hex retaining screw secures the rotor to the axleshaft flange.
Figure 6

An Allen-head/hex retaining screw secures the rotor to the axleshaft flange. (Some models use a Torx bolt.) This one broke loose with a hammer tap.

If the rotor won't lift off, check that the emergency brake isn't set.
Figure 7

If the rotor won't lift off, check that the emergency brake isn't set. Tapping the "hat" might break the rotor loose. (A rubber mallet is preferable to a brass hammer.) Other solutions include spraying penetrant between the rotor and axle shaft flange and retracting the e-brake shoes (please see our article on adjusting brake shoes).

Caliper removal doesn't require specialized tools or skill.
Figure 8

Caliper removal doesn't require specialized tools or skill. A punch is used to drive out the pad-retaining pins. This caliper is mounted with two 16mm bolts. The brake hose comes off with a 14mm flare wrench, and a G-clamp or vise-grips protected by a rag is helpful for pinching the brake hose closed.

An Allen wrench or hex bit and possibly a hammer are required to remove the R170 rear rotor.
Figure 9

An Allen wrench or hex bit and possibly a hammer are required to remove the R170 rear rotor. Anti-seize and brake cleaner are useful when installing the replacements.

Bookmark and Share
Comments and Suggestions:
Lou Comments: Do the same steps for rotor replacement and new pads in the rear apply to the front brakes for a 1999 SLK? I did not see any information for front brakes. Thanks.
April 6, 2016
  Followup from the Pelican Staff: The fronts should be similar, maybe a bit easier. Due to the flexibility of the suspension. I will see if I can have that article created. - Nick at Pelican Parts  

  Search our site:    

View Cart & CheckOut | Project List | Order Status |  Help    

 

[Home] [Customer Service] [Shopping Cart] [Project/Wish List]
  [Privacy Statement]  [Contact Us] [About Us] [Shipping] [Careers]

Copyright © Pelican Parts Inc. -    DMCA Registered Agent Contact Page

Page last updated: Wed 12/7/2016 02:26:24 AM