Jeep CJ/Scrambler 1971-1986 Repair Guide

Rotor (Disc)



See Figure 1

1977-1986 Models

Brake shoes contain asbestos, which has been determined to be a cancer causing agent. Never clean the brake surfaces with compressed air! Avoid inhaling any dust from any brake surface! When cleaning brake surfaces, use a commercially available brake cleaning fluid.

  1. Loosen the front wheel lug nuts. Raise and support the front end on jackstands.
  3. Remove the wheels.
  5. Remove the front hub grease cap and driving hub snapring. On models equipped with locking hubs, remove the retainer knob hub ring, agitator knob, snapring, outer clutch retaining ring and actuating cam body.
  7. Remove the splined driving hub and the pressure spring. This may require slight prying with a screwdriver.
  9. Remove the external snapring from the spindle shaft and remove the hub shaft drive gear.
  11. Remove the wheel bearing locknut, lockring, adjusting nut and inner lockring.
  13. Remove the caliper and suspend it out of the way by hanging it from a suspension or frame member with a length of wire. Do not disconnect the brake hose, and be careful to avoid stretching the hose. Remove the rotor and hub assembly. The outer wheel bearing and, on vehicles with locking hubs, the spring collar, will come off with the hub.
  15. If the old parts are retained, thoroughly clean them in a safe solvent and allow them to dry on a clean towel. Never spin dry them with compressed air.
  17. Cover the spindle with a cloth.
  19. Remove the cloth and thoroughly clean the spindle.
  21. Thoroughly clean the inside of the hub.
  23. Pack the inside of the hub with EP wheel bearing grease. Add grease to the hub until it is flush with the inside diameter of the bearing cup.
  25. Pack the bearing with the same grease. A needle-shaped wheel bearing packer is best for this operation. If one is not available, place a large amount of grease in the palm of your hand and slide the edge of the bearing cage through the grease to pick up as much as possible, then work the grease in as best you can with your fingers.
  27. If a new race is being installed, very carefully drive it into position until it bottoms all around, using a brass drift. Be careful to avoid scratching the surface.
  29. Place the inner bearing in the race and install a new grease seal.
  31. Place the hub assembly onto the spindle and install the inner lockring and outer bearing. Install the wheel bearing nut and torque it to 50 ft. lbs. while turning the wheel back and forth to seat the bearings. Back off the nut about 1 / 4 turn (90°) maximum.
  33. Install the lockwasher with the tab aligned with the keyway in the spindle and turn the inner wheel bearing adjusting nut until the peg on the nut engages the nearest hole in the lockwasher.
  35. Install the outer locknut and torque it to 50 ft. lbs.
  37. Install the spring collar, drive flange, snapring, pressure spring, and hub cap.
  39. Install the caliper over the rotor.

Click image to see an enlarged view

Fig. Fig. 1: Checking the rotor thickness variation


Check the rotor for surface cracks, nicks, broken cooling fins and scoring of both contact surfaces. Some scoring of the surfaces may occur during normal use. Scoring that is 0.009 in. (0.23mm) deep or less is not detrimental to the operation of the brakes.

If the rotor surface is heavily rusted or scaled, clean both surfaces on a disc brake lathe using flat sanding discs before attempting any measurements.

With the hub and rotor assembly mounted on the spindle of the vehicle or a disc brake lathe and all play removed from the wheel bearings, assemble a dial indicator so that the stem contacts the center of the rotor braking surface. Zero the dial indicator before taking any measurements. Lateral run-out must not exceed 0.005 in. (0.13mm) with a maximum rate of change not to exceed 0.001 in. (0.025mm) in 30 degrees of rotation. Excessive run-out will cause the rotor to wobble and knock the piston back into the caliper causing increased pedal travel, noise and vibration.

After the rotor has been refinished, the minimum thickness of 1.1207 in. (28.5mm) is acceptable for models through 1978; 0.815 in. (20.7mm) for 1979-86 models. Discard the rotor if the thickness is less.

Remember to adjust the wheel bearings after the run-out measurement has been taken.