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Rear Parking Brake Shoe Replacement
 
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Pelican Technical Article:

Rear Parking Brake Shoe Replacement

Tom Morr

Time:

3 hours3 hrs

Tab:

$29

Talent:

*****

Tools:

Needle-nose pliers, vise grips, flat blade screwdriver

Applicable Models:

Mercedes-Benz R170 (1998-04)

Parts Required:

New parking brake shoes

Hot Tip:

Thoroughly clean any components that will be re-used prior to reassembly

Performance Gain:

Car won't roll on hill

Complementary Modification:

Inspect and replace rear rotors and pads as necessary

The R170 SLK's parking/emergency brake system is similar to many other Mercedes-Benz models. It's actually a manual drum brake within the hydraulic disc system: The rotors' inner hubs serve as the drums, and pulling the parking-brake lever expands the shoes against the hub, theoretically preventing the rear wheels from moving. Mechanical parking brake systems are mandated by the DOT for street-driven vehicles. Should the primary hydraulic brakes leak or otherwise fail, the mechanical parking brake system theoretically remains an emergency Plan B.

The parking brake shoe linings eventually wear out. They can also become ineffective if coated in oil. Driving with the parking brake applied can also cause failure. The shoes can overheat, crack, and even crumble.

Replacing the R170 SLK's parking brakes is similar to doing a brake job on a car with drum brakes. Specialized tools are available to expedite the job. However, normal hand tools will work, but finesse and patience are often required. Stretching the springs between the shoes is the trickiest part. Eye protection should be worn in case the springs pop loose, and the car should obviously be raised and secured on jack stands. Highlights of the parking-brake replacement are shown below.

After replacing the shoes, there is a parking brake bed-in procedure. Driving on a secluded, dry road at 30 mph, the hand lever is applied two to three times until the car comes to a stop. Use a moderate amount of force on the lever. Alternately, the car can be driven at 30 mph with the parking brake applied for 10 seconds while applying a moderate amount of force on the parking brake lever.

If the car pulls to one side, check the adjuster screws and cable adjustments (please see our related article for details).

Replacement parking brake shoe kits come with new springs and caliper bolts.
Figure 1

Replacement parking brake shoe kits come with new springs and caliper bolts. Note that the friction lining on the new shoes is thicker than the metal lip it's bonded to.

Please see the article on caliper and rotor removal for details.
Figure 2

Please see the article on caliper and rotor removal for details. Once those components are out of the way and the brake-cable handle is down, spin the wheel hub until one of the access holes aligns with the spreader spring, near the top of the parking brake assembly. Use a flat blade screwdriver to unhook the spring (arrow).

The locating springs: one in the center of each shoe: each have a pigtail that hooks into the backing plate.
Figure 3

The locating springs: one in the center of each shoe: each have a pigtail that hooks into the backing plate. M-B makes a special tool for removing them (112-589-09-61-00-MBZ), but needle-nose pliers or a 7/16-inch socket on a nutdriver can also be used to depress the spring (arrow) and rotate it a quarter turn to detach it from the backing plate.

The shoes can now be unhooked from the upper spreader spring and lower return spring and lifted out from between the hub and backing plate.
Figure 4

The shoes can now be unhooked from the upper spreader spring and lower return spring and lifted out from between the hub and backing plate.

Here's an exploded look at the parking brake components.
Figure 5

Here's an exploded look at the parking brake components. The adjuster star wheel (arrow) is located at approximately the 1:00 position on the left side and 11:00 on the right side. Do one side at a time so the other side can be used for reference if necessary during re-assembly.

Thoroughly clean any components that will be re-used.
Figure 6

Thoroughly clean any components that will be re-used.

Lubricate the adjuster screw's and wheel's threads with grease, such as the Mercedes-Benz Long Term Grease (000-989-63-51-MBZ) or something comparable.
Figure 7

Lubricate the adjuster screw's and wheel's threads with grease, such as the Mercedes-Benz Long Term Grease (000-989-63-51-MBZ) or something comparable.

We're re-using the existing parts for demonstration purposes.
Figure 8

We're re-using the existing parts for demonstration purposes. Here's how the left side re-assembles, excluding the cable.

Each locating spring has a tail (red arrow) that hooks into a slot on the backing plate (yellow arrow).
Figure 9

Each locating spring has a tail (red arrow) that hooks into a slot on the backing plate (yellow arrow).

Removing the wheel hub is a pain and isn't necessary to replace the parking brake shoes; ours was already off to replace the wheel bearing.
Figure 10

Removing the wheel hub is a pain and isn't necessary to replace the parking brake shoes; ours was already off to replace the wheel bearing. Set the adjuster in the shoes' tangs with the star wheel (yellow arrow) facing the front of the vehicle. Then hook the spreader spring (red arrow) on the backside of the shoes and set the assembly over the knuckle.

The locating springs (arrows) are compressed with needle-nose pliers or another suitable tool until their tails can be hooked in the slots on the backing plate.
Figure 11

The locating springs (arrows) are compressed with needle-nose pliers or another suitable tool until their tails can be hooked in the slots on the backing plate.

The expanding lock (yellow arrow) can normally be left on the vehicle, attached to the cable.
Figure 12

The expanding lock (yellow arrow) can normally be left on the vehicle, attached to the cable. If removed, reattach the expanding lock to the cable's clevice using the OE pin (red arrow).

Insert the expanding lock's slots into the corresponding notches in the shoes (arrows).
Figure 13

Insert the expanding lock's slots into the corresponding notches in the shoes (arrows).

Spreading the return spring across the shoes' lower slots can be a challenge.
Figure 14

Spreading the return spring across the shoes' lower slots can be a challenge. A special tool is made specifically for the job (116-589-01-62-00-MBZ). We had success using locking needle-nose pliers.

The shoes slide on nubs on the backing plate.
Figure 15

The shoes slide on nubs on the backing plate. Greasing these areas improves parking brake performance. Be careful to keep grease off of the shoes' friction surfaces. We gently pried the shoes away from the backing plate and used a popsicle stick to apply dollops of long-term grease (arrow). Complete the job by installing the rotor and caliper and adjusting the parking brake shoes (and cable, if necessary).

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