We’ve covered disc brakes, so now it’s time to tackle drum brakes.
The principle of semi-circular shoes acting against the internals of a machined drum that rotates as part of the hub assembly provided adequate stopping power for many years.
In addition, the components are protected from dirt and debris – an important consideration on early roads.
As front disc brakes became prevalent, drums continued to provide rear-axle braking largely because they allow a simple and effective handbrake system.
To get short and confidence-inspiring pedal travel, the clearance between the friction surface and the drum has to be minimised.
Shoe position is usually altered via an adjuster nut on the outside of the backplate, connected to a snail cam or wedge-shaped spreader.
Other systems use a rotating collar – accessed through a hole in the front face of the drum – to extend a threaded rod.
Some later designs have automatic adjusters, which can need some assistance as they age – Mk1 VW Golfs are notorious for this failing. Check your handbook or workshop manual to see exactly which system your car has fitted.
Classic brake pads may contain asbestos – wear a face mask, and use brake cleaner to damp down dust.
STEP 1: REMOVE DRUM
With one axle supported and the other chocked, take off the wheel and slacken the adjuster screws.
Undo the transport screw or wheel-bearing retainer that holds the drum to the hub, then tap the drum to shock it free and pull it off with the aid of a lever.
Clean the drum with brake parts cleaner.
STEP 2: CHECK COMPONENTS
Offer up new shoes to work out exactly where each of the four in an axle set goes before you start dismantling.
Only strip down one side at a time, to leave a reference for reassembly. Make notes of which spring goes where, and take photos with a camera or mobile phone to use as further reference.
STEP 3: STRIP DOWN
Remove steady springs where fitted, then use a long lever bar to release shoes from the slots that locate them.
As the shoes drop towards the centre of the drum, the springs will slacken and they can be removed, laid down in order on a clean surface, cleaned and checked for wear and kinks.
STEP 4: CLEAN UP
Douse the backplate with brake cleaner and remove all brake dust. Use a wire brush to free stubborn deposits, then clean any corrosion where the shoes rub to provide a smooth surface.
Apply a thin smear of copper grease to allow the shoes to slide, but don’t overdo it or you may contaminate the friction lining.
STEP 5: CHECK WHEEL CYLINDERS
Peel back the rubber dust cover on the end(s) of the slave cylinder. Check that no brake fluid is getting past the seal inside the bore of the cylinder.
Use a screwdriver to push the piston(s) down to make sure that it isn’t seized. Replacement or rebuild is necessary if you can see any fluid, or if the piston is stuck.
STEP 6: REASSEMBLE
Refer to previous notes, photos and the other side of the axle. Put the shoes and springs back together.
A screwdriver with a vee ground into its end can help lever springs into position, and an upturned ¼in-drive socket is useful for replacing steady springs.
Clean out ratcheting self-adjusters with a wire brush.
STEP 7: ADJUST SHOES
Refit the drum and ensure the handbrake cables are partially slackened, then use the adjuster to put the shoes in contact with the drum on each side so it binds.
Slacken until the drum turns, then pump the brake hard to centralise and locate the shoes. Then re-adjust to minimise shoe-to-drum gap for a good firm pedal.
STEP 8: SET HANDBRAKE TRAVEL
With shoe clearances set, you can adjust the parking brake. You’ll find the adjusters on the linkage by the rear axle (live-axle cars), mounted as part of the inner/outer front-to-rear cable (some Fords and others) or at the handbrake end.
Set to maker’s clearance, usually around 4-7 clicks and with plenty of reserve travel.
Specialists and useful contacts
- Typecast Engineering (bespoke drums)
- Sealey Tools
- Laser Tools
- Kenway Workshop Consumables