16-11-2012, 04:46 PM
Disc brakes
Disc brakes.ppt (Size: 1.71 MB / Downloads: 91)
Disc brakes use hydraulic pressure to clamp brake pads against a rotating disc called a rotor
Most vehicles have front wheel discs, some have discs on all 4 wheels
Disc brakes use the friction between the rotor and brake pads to stop the vehicle
This also creates a lot of heat
Disc brakes, however, can release all this heat better than drums – because they are open and not enclosed in a drum – air can flow over these parts and cool them
Water is also dispeled as well, making wet braking much more effective
Have 4 main components:
Brake pads – provide friction to stop
Rotors – metal discs that rub against the pads to stop
Calipers – housings that contain the pistons and the brake pads
Caliper mounting brackets – hold the calipers in place on the car
Brake pads
Provide friction
Are flat steel plates with friction material, called linings, attached by rivets or adhesive
Pads are inside the caliper housing
Pushed against the rotor by the pistons inside the caliper
Can be made of metallic, organic, ceramic or carbon
When the brakes are applied, the pads create high braking forces on both sides of the rotor
This causes a lot of heat, but since the rotor is exposed to air, it is released quickly
This allows the brakes to absorb and dissipate heat much better than drums
Brake rotors
Rotors are round, flat disc shaped devices made from cat iron, sintered iron, or an alloy – some are even carbon or ceramic
They are attached to the vehicle by a spindle or a hub, and a wheel bearing
There are 2 types – vented and solid
Vented rotors have fins in the space between the 2 machined surfaces
The fins allow air to pass through the rotor
This carries away the heat build up, and allows better braking
They can also be slotted or cross-drilled – again for airflow and heat dissipation
Fixed caliper disc brakes
Fixed caliper means that the caliper is in a fixed position and cannot move
The caliper has pistons on both sides of the rotor – 2, 4, 6 or 8 in total
The pistons are the moving parts – they push the pad into the rotor to stop
Used in high performance cars
Floating caliper brakes
The caliper is free to move side to side on bushings or guide pins – attached to the spindle or carrier
Usually contain only 1 piston
The piston applies pressure to the inboard pad – as the pad touches the rotor the caliper slides on the pins, and pulls the outboard pad into the rotor as well
The pads have zero clearance to the rotor