Brakes Disc Drums

Discs or drums?
Braking creates a lot of heat which has to be dispelled fast. The more open design of disc brakes makes them much less susceptible to overheating.

It’s normal to see discs at the front – providing most of the braking effort – and cheaper drum brakes on the rear to provide the parking brake function. Larger or more powerful cars tend to have disc brakes on all four corners.

Parking brake
Some cars with ‘discs all round’ will have been fitted with a small drum brake in the centre of the rear hubs for the parking brake, though most now work by applying pads directly to the main discs

Electrically operated parking brakes may take a while to get used to. The handbook will show a special release procedure to use if the car battery is flat.

Corrosion
Cast iron is an ideal material for brake components, but it rusts easily.
On the front, surface rust is quickly cleaned off by the action of the pads on the discs, but this may not be the case on the rear, especially on a small, light vehicle or one only used infrequently and for local trips.
Corrosion isn’t normally a problem with rear drum brakes.
Initial, light corrosion can be cleaned off under reasonably heavy braking, but if left, this light corrosion gets worse and can lead to surface pitting.
Pitting used to be a reason for MOT test failure, but now discs should only fail the test if they’ve become ‘seriously weakened’.
Surface corrosion or pitting of discs isn’t a ‘fitness for purpose’ or warranty repair issue, as it mainly depends on how the vehicle is used and stored.