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What is the braking system/what does it do?

The braking system varies on different makes and models. It may consist of a drum brake type system on all four wheels, rear drum brakes with disc brakes on the front wheels or disc brakes on all four wheels. Sometimes on the latter the hand brake system is of a drum type incorporated in the rear wheel discs. All of these systems operate using hydraulics. When the brake pedal is pressed it depresses a piston in the master cylinder forcing fluid along the brake piping to a slave cylinder at each wheel which bring into operation the brake shoes or disc pads.

Getting into the details of the braking system

These various systems entail various combinations of hydraulic fluid, brake pipes, master cylinders, slave cylinders, servos, brake pipes, brake drums, brake shoes, brake discs, brake pads, brake calipers, heat shields and various electronic warning and control devices to prevent wheel locking under heavy braking. The hydraulic system may be aided by a brake air servo, this is a device which uses the vacuum from the inlet manifold to operate a diaphragm which when activated by brake operation triggers the influx of outside air to one side of the vacuum and moves the diaphragm which assists the movement of the slave cylinder.

Drum brakes consist of a hollow drum to which the wheel is fixed.The drum and wheel revolve around a stationary backplate to which are fixed  two curved metal shoes which have brake linings made of a heat proof material. The shoes have a pivotal mounting at one end and  hydraulic pistons at the other, when the brakes are applied the shoes are forced outwards by the slave cylinders and lining of the shoes are pressed against the smooth inside of the drum, consequently slowing the spinning of the wheels.

Disc brakes, instead of the drum, have a disc to which the wheel is fixed, the disc is straddled by the brake caliper which holds the slave cylinder and the brake pads either side of the disc. The pads are metal pieces with a friction pad of heat proof material attached, the pads cover a broad section of the disc. When the brakes are applied the pads are forced hydraulically against the disc consequently slowing the spinning of the wheels. The pistons in the slave cylinder move only a fraction as the pads are positioned to just clear the disc, when the brake is released the pads move back to just clear the discs.

Additionally all vehicles are fitted with a handbrake, this is a cable operated system which can be used in an emergency but is primarily used as a parking brake. This is operated from the hand lever next to the driving position and is a lever pulling two cables which operate the rear wheel brake pads or brake shoes mechanically as opposed to hydraulically.

What if something goes wrong with the braking system?

Indications of faults in the braking system are, in modern cars signaled through warning lights and messages. A lowered performance in braking, noises when applying the brakes and any handling problems arising during braking are signs that the braking system needs checking.

The commonest serviceable parts of the braking system are the brake pads and brake shoes as these wear due to their usage which involves high heat and friction, also wearing at a slower rate are the drums and discs. Care must be taken to ensure that the reservoir of hydraulic fluid is kept at the necessary level, as if the level is allowed to drop to low air will be sucked into the system resulting in brake failure. Any significant  loss of fluid is a sign of failure in some part of the system.

Due to  the high energy forces, heat, friction and stresses involved with the braking system in the area of the discs and wheels it is of the utmost importance that all components are in good order.