DRUM BRAKES

D1 Drum brakes have their friction components enclosed and an internal set of friction shoes are pushed outwards to contact the inside face of a hub-located rotating drum. Some drums are held in place by several small screws.

D2 Older cars had drum brakes on the front and rear, while some modern cars have them on the rear only. Self-adjusting mechanisms are now universal – as the linings wore on older cars, periodic manual clearance adjustment was necessary (as shown).

D3 Some drums are held in place by a central hub nut. The drum is likely to incorporate the wheel bearing in these cases. On most cars, you must fit a new central nut and tighten it to the specified torque.

D4 As the friction linings are enclosed, the drums are likely to be dusty inside. As with disc brakes, you must not inhale it (especially on classic cars, where asbestos is likely to be present) but use brake cleaner to clean out the deposits.

D5 One particular issue with drum brakes is leaking slave cylinders. Not only does this cause poor braking performance, but bad leaks can be spotted by brake fluid dripping behind the rear back-plate when viewed beneath the car.

D6 Once the drum has been removed, you can identify a failed cylinder very quickly. Unfortunately, the brake fluid tends to be sprayed around the drum brake internals, mixing with the dust to create a messy and slippery paste.

D7 The friction linings also absorb brake fluid – this example was so bad that the linings had started to come away from their backing. As a result, both sets of axle brake shoes had to be renewed.

D8 Brake shoes tend to be retained by a variety of pins, springs and/or locking plates – the precise arrangement varies between vehicle models. They are also connected together by return springs, so note their positions before dismantling.

D9 The procedure for replacing hydraulic cylinders differs, too. This one is held to the back-plate by a pair of horseshoe clips. It is not worth resealing old cylinders. Consider replacing the hydraulics on the opposite side, too.

D10 Refitting brake shoes is fiddly, as they need to be positioned together with their return springs. Some suppliers (such as Borg and Beck) sell pre-assembled shoes for some models, which are far easier to install, especially for a DIYER.

D11 Pictured are the reassembled drum linings, ready for the drum to be fitted. Self-adjustment tends to be performed by pulling the handbrake lever, otherwise you can manipulate the adjustment ratchet manually (see Step D14).

D12 Some cars are fitted with a hydraulic disc brake on the rear. A set of handbrake shoes – fitted within a hollow centre hub – are operated mechanically by the handbrake lever.

D13 Pictured is a close-up of this handbrake-only design showing the brake shoes, their retaining pins and clips, and a return spring. Obviously, it lacks hydraulic components and, for this reason, handbrake-only drums tend to be neglected.

D14 Pictured are the auto-adjuster teeth. When the handbrake lever travel is excessive and the shoes are in good condition, check that this part has not seized, due to corrosion and dust ingress, by turning with a screwdriver.