Automotive Disc Brakes

Disc BrakesDisc brakes are fairly simple to work with, once you know the parts and their functions. Typically, there are 4 main parts of a system:Mounting BracketRotorCaliperPads

Mounting BracketsMounting Brackets are used to hold the Caliper in place. Other than keeping the surface clean and free of rust and road grime, there is very little to be done with this part

RotorsRotors are metal discs supported by the suspension. The Calipers clamp on to them to slow their rotation, and then slow or stop the car

Vented RotorThese are the VENTS

Vented RotorsVented Rotors have Fins in the spaces between their machined surfaces. These spaces allow air to pass through, which helps carry heat away.

Nonvented RotorNon Vented Rotors are used on smaller vehicles, and have no cooling fins

Non Vented Rotor

Rotor RepairWe will get back to these Rotors later concerning what you can do as a repair on them.

CalipersCalipers are the housings that contain the Pistons and the Brake Pads. The Calipers are connected to the Hydraulic System, and hold the brake pads to the Rotor

Caliper TypesThere are 2 types of Calipers

Fixed

Floating

Fixed CaliperFixed Calipers are disc brakes that use a caliper that is FIXED in position and does not slide. They have pistons on both sides of the disc. There may be 2 or 4 pistons per caliper

Fixed CaliperMotorcycles and some import trucks and cars use this type

Sliding CaliperMuch more commonSingle PistonEasier to work withOn inboard side of caliper

Clean, Floating Caliper

Floating Calipers

OperationPiston applies pressure to Inboard pad. As the pad contacts the rotor, the caliper slides along the pins, pulling the outboard pad into contact.CaliperRotorPistonBrake PadsBrake Line

Sliding caliper in operation

Parts of a Caliper

SealThe rebuild kit will have a new O ring, and a Dust Seal

PistonThe Piston surface should be smooth and clean. This one is pitted, and needs replaced.

Adjustments?Disc Brakes will automatically self-adjust. As the Pads wear, the caliper piston will not retract as farThis leaves a larger amount of brake fluid in the caliper, causing the master cylinder level to lower

Caliper SlidesNotice where the brake pads and calipers slide on the pin and the mount

Caliper slidesSince parts need to slide, these areas should be clean of dirt and rust,

Cleaning CaliperWith the caliper off, I would use a wire brush to clean the rust off, then use a brake cleaning solvent to wash the sliding area.

Wear IndicatorsBrake pads wear, and most people never check them. So, something was put on the pads to make a noise, since most people will have a noise checked out.

Brake NoiseWear Indicator

Brake PulsationUsually a warped RotorRotor needs trued on a brake lathe