Rear brake drum - removal, inspection and refitting

Braking system / Rear brake drum - removal, inspection and refitting

Note: Before starting work, refer to the warning at the beginning of Section 5 concerning the dangers of asbestos dust.

Removal
1 Chock the front wheels, then jack up the rear of the vehicle and support it on axle stands (see “Jacking and vehicle support”).

Remove the appropriate rear wheel. Release the handbrake lever.

2 Using a hammer and a large flat-bladed screwdriver, carefully tap and prise the cap out of the centre of the brake drum (see illustration). Discard the cap if it is disfigured during removal.

7.2 Lever out and remove the cap from the centre of the brake drum

3 Extract the split pin and remove the locking cap (see illustrations). Discard the split pin; a new one must be used on refitting.

7.3a Remove the split pin . . .

7.3b . . . and locking cap.. .

4 Unscrew and remove the rear hub nut, then slide off the toothed washer and remove the outer bearing from the centre of the drum (see illustrations).

7.4a . . . then unscrew the retaining nut. . .

7.4b . . . remove the toothed washer. . .

7.4c . . . and withdraw the outer bearing

5 It should now be possible to withdraw the brake drum assembly from the stub axle by hand (see illustration). However it may be difficult to remove the drum, due to the tightness of the hub bearing on the stub axle, or due to the brake shoes binding on the inner circumference of the drum. If the bearing is tight, tap the periphery of the drum using a hide or plastic mallet, or use a universal puller, secured to the drum with the wheel bolts, to pull it off. If the brake shoes are binding, first check that the handbrake is fully released, then continue as follows.

7.5 . . . and remove the brake drum

6 Check that the handbrake is fully released.

7 Insert a screwdriver through one of the wheel bolt holes in the brake drum, and lever up the wedge key in order to allow the brake shoes to retract fully (see illustration). The brake drum can now be withdrawn.

7.7 Release the brake shoes by inserting a screwdriver through the drum hole

Inspection
Note: If either drum requires renewal, BOTH should be renewed at the same time, to ensure even and consistent braking. New brake shoes should also be fitted.

8 working carefully, remove all traces of brake dust from the drum, but avoid inhaling the dust as it may contain asbestos and be injurious to health.

9 Clean the outside of the drum, and check it for obvious signs of wear or damage, such as cracks around the roadwheel bolt holes; renew the drum if necessary.

10 Examine the inside of the drum. Light scoring of the friction surface is normal, but if heavy scoring is found, the drum must be renewed. It is usual to find a lip on the drum’s inboard edge which consists of a mixture of rust and brake dust; this should be scraped away.

11 If the drum is thought to be excessively worn, or oval, its internal diameter must be measured at several points using an internal micrometer. Take measurements in pairs, the second at right-angles to the first, and compare the two, to check for signs of ovality.

Provided that it does not enlarge the drum to beyond the specified maximum diameter, it may be possible to have the drum refinished by skimming or grinding; if this is not possible, the drums on both sides must be renewed.

Note that if the drum is to be skimmed, BOTH drums must be refinished to maintain a consistent internal diameter on both sides.

Refitting
12 If new brake drums are to be installed, use a suitable solvent to remove any preservative coating that may have been applied to the friction surfaces. If necessary, install the bearing races, inner bearing and oil seal as described in Chapter 10, and thoroughly grease the outer bearing.

13 Prior to refitting, fully retract the brake shoes by lifting up the wedge key.

14 Apply a smear of grease to the drum oil seal, and carefully slide the assembly onto the stub axle.

1 5 Fit the outer bearing and toothed thrustwasher, ensuring its tooth is correctly engaged in the axle slot.

16 Refit the hub nut and moderately tighten it whilst rotating the brake drum to settle the hub bearings in position. Gradually slacken the hub nut until the position is found where it is just possible to move the toothed washer from side-to-side using a screwdriver (see illustration). Note: On/y finger pressure should be needed to move the washer. Do not turn or /ever the screwdriver. When the hub nut is correctly positioned, refit the locking cap and secure the nut in position with a new split pin.

7.16 Checking the adjustment of the rear hub bearing with a screwdriver

17 Fit the cap to the centre of the brake drum, tapping it fully into position with a light hammer.

18 Depress the footbrake several times to operate the self-adjusting mechanism.

19 Repeat the above procedure on the remaining rear brake assembly (where necessary), then check and if necessary adjust the handbrake cable (see Section 14).

20 On completion, refit the roadwheel( then lower the vehicle to the ground and tighten the wheel bolts to the specified torque.