A drum brake has a hole drum that turns with the wheel. Its open again is included by way of a stationary backplate on which there are two curved sneakers carrying friction linings.
The footwear are pressured outwards with the aid of hydraulic pressure moving pistons within the brake’s wheel cylinders, so urgent the linings in opposition to the inside of the drum to slow or discontinue it.
With the brakes on, the footwear are pressured towards the drums by way of their piston.
Every brake shoe has a pivot at one finish and a piston at the different. A leading shoe has the piston on the leading part relative to the direction in which the drum turns.
The rotation of the drum tends to drag the main shoe firmly against it when it makes contact, improving the braking result.
Some drums have twin leading sneakers, every with its possess hydraulic cylinder; others have one leading and one trailing shoe – with the pivot at the front.
This design allows for the two footwear to be forced apart from each and every different by means of a single cylinder with a piston in each finish.
It is less difficult but much less robust than the 2-leading-shoe approach, and is typically limited to rear brakes.
In both kind, return springs pull the footwear again a short method when the brakes are launched.
Shoe travel is stored as short as possible by means of an adjuster. Older methods have manual adjusters that need to be became every so often because the friction linings put on. Later brakes have computerized adjustment by means of a ratchet.
Drum brakes could fade if they are utilized many times within a short time – they heat up and lose their effectivity until they settle down once more. Discs, with their extra open construction, are a lot much less susceptible to fading.
The handbrake mechanism
The handbrake acts on the footwear by way of a mechanical approach, separate from the hydraulic cylinder, together with a lever and arm in the brake drum; they’re operated by a cable from the handbrake lever within the car.
Aside from the hydraulic braking approach, all cars have a mechanical handbrake appearing on two wheels – commonly the rear ones.
The handbrake gives restrained braking if the hydraulic method fails wholly, but its main reason is as a parking brake.
The handbrake lever pulls a cable or pair of cables linked to the brakes through a set of smaller levers, pulleys and guides whose small print vary generally from vehicle to auto.
A ratchet on the handbrake lever keeps the brake on once it’s utilized. A push button disengages the ratchet and frees the lever.
On drum brakes, the handbrake method presses the brake linings against the drums.
Disc brakes regularly have a related handbrake association, however considering that it’s intricate to location the linkage on a compact caliper, there could also be a fully separate set of handbrake pads for each and every disc.