Brake Systems

A brake system is used to slow or stop a vehicle in motion.  To do this, it uses friction at the wheels to convert momentum into heat energy.  The system works to slow or stop the rotation of the wheels.

Two types of friction are at work in brake systems: kinetic and static.  Kinetic friction produces heat from the momentum of the vehicle as brakes slow or stop it.  Kinetic friction is related to movement and static friction is related to a stationary or stopped vehicle.  Static fiction holds a vehicle in place once it has come to a stop.

A hydraulic braking system uses brake fluid to transfer pressure to brake pads or shoes.  This is done by pressing on the brake pedal.  Pressure from a hydraulic system transmits the amount of pressure applied in pounds per square inch (psi) equally to all other parts of that system.  However, by changing the size of a piston hydraulic pressure can be increased or decreased at the outlet.  In this way, it transfers the force of pressing in the pedal to the force needed to slow or stop the wheels.

In a drum brake system brake shoes press against a brake drum to slow and stop the vehicle.  In a disc brake system brake pads are used in an actuated system which uses brake calipers to apply pressure to a brake rotor.

Inspecting brake systems is necessary for the safe operation of a vehicle.  To do so, begin by checking the condition of the brake fluid in the master cylinder.  If the fluid is cloudy, or thick, or appears to be dirty and separated into layers assume it has been contaminated.  Brake fluid should be flushed and refilled about every 2 years.   If brake fluid is low, this can be a sign of an external leak or a sign that the brake linings are worn.  Check all tubing, hoses, and connections for leaks, damage, and weak areas.  Hoses should be checked for flexibility, bulges, and cracks.  In addition, the brake pedal should depress and release smoothly and pedal action should be firm.

Antilock brake systems pump the brakes for stopping under duress.  Holding the brake pedal down and apply heavy immediate pressure can cause the vehicle brakes to lock up and skid.  The antilock brake system can prevent this from happening.

Erjavec, Jack and Thompson, Rob.  Automotive Technology: A Systems Approach.  6th Edition, (2015). Pg. 1467-1557.