Disk Brakes

Disk brakes fairly easy to understand.  The main objective of the braking system is to decrease the speed of a vehicle.  Some vehicles have drum brakes in the rear and disks on the front.  However, most vehicles today are equip with disk brakes in both front and rear.

Disk Brakes

The disk, or rotor themselves are just a small part of the braking system.   The disc brake system has a disc that turns with the wheel.  A caliper has a hydraulic piston that  works by pressure from the master cylinder. Thus,  the caliper rides on the disk and moves the brake pads into the disk when the brake pedal is pushed in.  As a result, the vehicle will decrease in speed.

disk brakes
Diagram by: K.D. Schroeder

Eventually, as the pads wear down the caliper’s piston adjusts automatically.  Wear sensors on the pads will alert the driver then the brake pads need service.  Reinforced carbon, ceramic composites, or cast iron rotors can take the heat from friction. Therefore, a simple resurfacing can usually bring them back to new condition.


Power Assisted Disk Brakes

power disk brake All new cars and trucks today are equip with power brakes.  Power brakes make stopping effortless.  The brake booster is the most important element of power brake system.

A rod opens a valve when the brake pedal is down.  Air moves into the booster on one side while sealing off the vacuum.  By increasing pressure on one side of the diaphragm, the rod moves into the piston inside the master cylinder.

The Master Cylinder

Diagram by: Fred the Oyster

moving a piston inside the bore of the master cylinder creates hydraulic pressure to the rest of the brake system.  The master cylinder has two circuits so that, if one fails the other will still function.  Each circuit has brake fluid that it supplies to the system.  The fluid contained inside a reservoir sits on top of the master cylinder and is fed into each circuit.

What is Brake Fluid?

Brake fluid is a special liquid for use in hydraulic brake systems.  Brake fluid will adjust to wide temperature changes and not boil, even in extreme temperatures.  There are different types of brake fluid.  Most cars use “DOT 3” or “DOT 4” brake fluid.  On the other hand, some newer cars use silicone brake fluid.

Being that the seals in each car are designed to work with only their specific fluid type, the right fluid must be used to avoid contamination.  “System contamination” means that all of the piston seals and hoses are deteriorating.  As a result, brake service will be expensive to replace these parts.