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Front Brake Rotor Replacement
 
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Pelican Technical Article:

Front Brake Rotor Replacement

Steve Vernon

Time:

2 hours2 hrs

Tab:

$30 to $100

Talent:

**

Tools:

10mm, 5mm Allen, breaker bar, large pliers, friend

Applicable Models:

Mercedes-Benz W123 (1977-85)

Parts Required:

Rotors

Hot Tip:

Pre-soak rusted bolts in penetrant oil

Performance Gain:

Car stops better

Complementary Modification:

Flush and bleed brake system

Replacing your brake rotors is an easy job to perform on your Mercedes-Benz W123 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. The rotor can also get heat sunk by excessive short term stops and then sitting with the brake pads fully depressed on the rotor. This will cause the rotor to eventually warp and cause a pulsing sensation when braking.

If you ignore the brake pad 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. Rotors should always be replaced in pairs.

NOTE: If your rotors are really grooved you should replace your brake pads as well.

Begin by safely jacking up and supporting the vehicle and removing the front wheels and remove the calipers.
Figure 1

Begin by safely jacking up and supporting the vehicle and removing the front wheels and remove the calipers. Please see our article on jacking up and supporting your W123 along with removing your brake caliper.

Use a large set of pliers or a punch and remove the grease cap from the end of the hub.
Figure 2

Use a large set of pliers or a punch and remove the grease cap from the end of the hub.

Next use a 5mm Allen and loosen the pinch nut on the end of the spindle (red arrow).
Figure 3

Next use a 5mm Allen and loosen the pinch nut on the end of the spindle (red arrow).

Unscrew and remove the pinch nut from the end of the spindle.
Figure 4

Unscrew and remove the pinch nut from the end of the spindle.

Lightly pull the rotor a little forward and remove the outer bearing, if you end up pulling the rotor completely off make sure you catch the bearing so it doesn't hit the ground.
Figure 5

Lightly pull the rotor a little forward and remove the outer bearing, if you end up pulling the rotor completely off make sure you catch the bearing so it doesn't hit the ground.

Remove the hub and rotor from the spindle (red arrow).
Figure 6

Remove the hub and rotor from the spindle (red arrow). Inspect the spindle for any damage, this would include burs, gouges, scratches or heat damage.

You are going to need to remove the five 10mm Allen bolts that attach the rotor to the hub (red arrow).
Figure 7

You are going to need to remove the five 10mm Allen bolts that attach the rotor to the hub (red arrow).

The rotor is attached to the hub with a fair amount of torque and usually some blue Loctite.
Figure 8

The rotor is attached to the hub with a fair amount of torque and usually some blue Loctite. One trick to getting the bolts off is to hit them with some penetrating oil and then attach the hub to the wheel with three bolts. You can either lay the wheel on the floor and have a friend stand on it or position the wheel upright against a wall and break the bolts free that way.

With the bolts removed the rotor will easily separate from the hub.
Figure 9

With the bolts removed the rotor will easily separate from the hub.

Make sure to clean the mounting surface on the hub before installing the new rotor; you want a nice clean and flat mounting surface (red arrow).
Figure 10

Make sure to clean the mounting surface on the hub before installing the new rotor; you want a nice clean and flat mounting surface (red arrow). Installation is the reverse of removal.

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Comments and Suggestions:
GasDonkey Comments: How do you set the proper torque spec on the pinch nut?
April 1, 2017
  Followup from the Pelican Staff: I don’t have torque information.

I would suggest you grab a repair manual, you should own one. It will have the procedure, special tools and torque specs.

Give our parts specialists a call at 1-888-280-7799. - Nick at Pelican Parts
 

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Page last updated: Sat 4/29/2017 03:11:08 AM