Mazda Trucks 1972-1986 Repair Guide

Brake Disc (Rotor)

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REMOVAL & INSTALLATION



See Figures 1 through 12

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Fig. Fig. 1: Use a dial indicator to check disc run-out



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Fig. Fig. 2: Using a micrometer to measure the rotor thickness



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Fig. Fig. 3: Example of excessive run-out, which can cause brake pedal pulsation



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Fig. Fig. 4: Measure the rotor at several points and compare the readings to determine parallelism



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Fig. Fig. 5: These surfaces should be flat and within 0.002 in.



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Fig. Fig. 6: Taper variation should not exceed 0.003 in.



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Fig. Fig. 7: Aligning matchmarks for rotor assembly



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Fig. Fig. 8: Fill the hub flush with grease



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Fig. Fig. 9: Pack the bearing with clean grease



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Fig. Fig. 10: Checking bearing preload with a spring scale



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Fig. Fig. 11: Setting bearing preload



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Fig. Fig. 12: Tightening the caliper mounting bolts

  1. Raise and support the front end on jackstands.
  2.  
  3. Remove the wheel.
  4.  
  5. Remove the grease cap, cotter pin, hub nut and flat washer.
  6.  
  7. Remove the caliper and suspend it out of the way without disconnecting the brake line. At this point, check the disc runout using a dial indicator. Slowly pull the hub from the spindle, positioning your hand to catch the outer bearing.
  8.  
  9. Matchmark the hub and rotor. Unbolt the rotor from the hub.
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  11. Inspect the rotor for any signs of wear, damage, roughness, ridges, pitting or heat discoloration. If heat discoloration is noted, you probably have a problem with the caliper piston seizing. Rebuild the caliper. Check the rotor thickness. To correct most of the above problems, have the rotor turned at a machine shop. Minimum rotor thickness is 11mm (0.433 in.).
  12.  
  13. When installing the rotor, make sure that the matchmarks are aligned. Tighten the rotor-to-hub bolts to 40 ft. lbs.
  14.  
  15. Pack the inside of the hub with clean wheel bearing grease until it is flush packed.
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  17. Pack the bearing with clean grease, making sure that it is thoroughly packed. Special devices are sold for packing bearings. They are inexpensive and readily available. If you don't have one, just make certain that the bearing is as full of grease as possible by working it in with your fingers.
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  19. If removed, install the inner bearing and seal. Drive the seal into place carefully until it is seated.
  20.  
  21. Install the spacer and the hub on the spindle.
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  23. Install the outer bearing, flat washer and hub nut. Torque the nut to 22 ft. lbs. and turn the hub 2 or 3 times to seat the bearings. Back off the nut until it is loose. Rock the hub back and forth to make sure the pads are not causing any drag on the rotor. It may be necessary to force the inner pad back using a C-clamp.
  24.  
  25. Attach a spring scale to a wheel lug.
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  27. Pull the scale horizontally and check the force needed to start the wheel turning. The force should be 1.3-2.4 lbs. If the reading is not correct, tighten or loosen the hub nut until the correct pull rating is obtained.
  28.  
  29. Install the nut cap, cotter pin and grease cap. Install the wheel.
  30.  

 
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