BMW Coupes and Sedans 1970-1988 Repair Guide

Brake Discs

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REMOVAL & INSTALLATION



1977-83 Models
  1. Remove the rear wheel.
  2.  
  3. Remove the caliper as described in this section.
  4.  
  5. If equipped with an Allen head bolt on the hub cap of the disc, remove the Allen bolt and remove the disc. If this is no Allen bolt present, the disc simple pulls off the shaft. Note the position of the holes in the disc and axle shaft flange.
  6.  
  7. Reverse the removal procedure to install. Torque Allen bolts retaining the disc to 22-24 ft. lbs. (29-31 Nm).
  8.  

1984-88 Models
  1. Raise and support the vehicle. Remove the rear wheels.
  2.  
  3. Remove the caliper without disconnecting the brake line. Hang the caliper with a piece of wire so no tension is put on the brake line.
  4.  
  5. Remove the internal hex bolt from the hub and pull the rotor off the hub.
  6.  
  7. Check the rotor and replace as necessary.
  8.  

To install:
  1. Install the rotor and caliper. Install the wheels. Adjust the parking brake.
  2.  
  3. Burnish the rotors by making 5 full stops from 30 mph (50 kmph), then allow the brakes to cool. Make 5 additional stops from 30 mph (50 kmph) and allow the brakes to cool again. This will burnish the rotors and allow full braking efficiency.
  4.  

INSPECTION



  1. Mount a dial indicator on the rear caliper with the pin against the disc. It may be convenient to pull the rear brake pads out and measure between the jaws of the caliper.
  2.  
  3. Measure the thickness of the disc at eight points around the diameter on the worn surfaces with a micrometer. Compare the thickness readings and subtract the lowest from the highest. If this figure is greater than the maximum specification described in the specification chart at the beginning of this section, the disc must be machined. Note also the minimum thickness figures. If the disc requires machining and cannot be cleaned up before the thickness drops below the minimum figure, it must be replaced.
  4.  
  5. Preload the dial indicator a small amount and measure the total runout of the disc as it rotates. Compare with specifications and if runout is excessive, have the disc machined.
  6.  

 
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