The brake system is the most important system on our car.If your brakes don’t work properly, the result can be disastrous.So good brakes are essential for safety.
There are two completely idependent braking system on a car. One is the service brake. And the other is parking brake.The service brake is system is the main braking system used to stop or slow down your car during normal driving.It is operated by the driver depressing and releasing the brake pedal.The parking brake ‘s purposes are to hold a car stationary while it is unattended, and to keep the car from rolling on unleveled ground.I t is also called the hand brake.
Basically, all car brakes are friction brakes. When the driver applies the brake, the control device forces brake shoes, or pads, agsinst the rotating brake drums or disks at wheels.Friction between the shoes or pads and the drums or disks then slows or stops the wheels so that the car is braked.
Disk brske
The disk brake is the best brake we have found so far.In recent years, brakes have changed greatly in design. Disk brakes, used fro years for front wheel application,are fast replacing drum brakes on the rear wheels of modern cars. This is is generally due to their simpler design, lighter weight and better braking performance. The greatest advantage of disk is that they provide significantly better resistance to “brake fade” compared to drum type braking system.
The main components of a disk brake are ; brake pads, caliper (which contains a piston) and disk or rotor(which is mounted to the hub).
The disk brake is a lot like the brakes on a bicyle.Bicycle brakes have a caliper, which squeezes the brake pads against the wheel.In a disk brake, the brake pads squeeze the rotor instead of the wheel, and the froce is transmitted hydraulically instead of through a cable. Friction between the pads and the disk slows the disk down.
Brake pad
There are two brake pads on each caliper.They are constructed of a metal “shoe” with the lining riveted or bonded to it. The pads are mounted in the caliper, one on each side of the rotor. Brake linings used to be made primarily of asbestos because of its heat absorbing propeties and quiet operation.However, due to health risk, asbestos has been outlawed, so new materials are being used.
Caliper
There are two main types of calipers: floating calipers and fixed caliper.Calipers must be replaced if they show signs of leaking brake fluid.
Single piston floating calipers are the most popular and also least costly to manufacture and service.A floating caliper “float” or moves in a track in its support so that it can center itself over the rotor. As you apply brake pressure, the hydraulic fluid pushes in two directions.It forces the piston against the inner pad which in turn pushes against the rotor.It also pushes the caliper in the opposite direction agsinst the other side of the rotor. Floating calipers are also available on some vehicle with two piston mounted on tha same side.Two-piston-floating calipers are found on more expensive cars and can provide an improved braking “feel”.
Four-piston-fixed calipers are mounted rigidly to the support and are not allowed to move. Instead, there are two pistons on each side that press the pads against the rotor.Four-piston calipers have a better feel and are more efficient, but are more expensive to produce and cost more to service. This type of caliper is usually found on more expensive luxury and high performance cars.
Disk rotor
The disk rotor is made of iron with highly machined surfaces where the brake pads contact it. Just as the brake pads wear out over time, the rotor also undergoes some wear, usually in the form of rigies and groves where the brake pad rubs against it. This wear pattern exactly matches the wear pattern of the pads as they seat themselves to the rotor.When the pads are replaced, the rotor must be machined smooth to allow the new pads to have an event contact surface to work with.
Drum brake
So if disk brakes are so graet, how come we still have cars with drum brakes? The reason is cost, While all vehicles produced for many years have disk brakes on the front, drum brakes are cheaper to produce for the rear wheels.The main reason is the parking brake system.
Drum brakes consist of a backing plate, brack shoes, brake drum, brake drum, wheel cylinder, return springs and an automatic or self-adjusting system. When you apply the brakes, brake fluid is forced, under pressure, into the wheel cylinder which, in turn, pushes the brake shoes into contact with the machined surface on the inside of the drum.When the pressure is released, return springs pull the shoes back totheir rest position.As the brake linings wear, the shoes must travel a greater diatance to reach the drum.When the distance reaches a certain point, a self-adjusting mechanism automatically reacts by adjusting the rest position of the shoes so that they are closer to the drum.
auther:Candywww.sinodiesel.com
