How Brakes Work

 

The driver presses on the pedal and the trailer stops. But there’s quite a bit going on, and understanding it more fully can really help you get the most out of your brake system.
 
Here’s what’s going on:
 
The driver presses on the brake pedal, the surge of you stopping actuates the piston in the master cylinder (MC). If you have electric/hydraulic actuator the electric signal ramps up the motor and builds pressure.  The piston in the master cylinder displaces the hydraulic fluid in the brake lines. Because the system is sealed, the displacement (movement) of the hydraulic fluid moves the piston(s) in the brake calipers.  The moving calipers bring the brake pads into contact with the rotor. At this point, because there is no more movement possible in the system, pressure begins to build, and the pads are pressed harder and harder against the rotor, creating friction, and stopping the trailer.
 
In summary, in order to stop the trailer, the brakes must have three properties. They must:
  1. Be able to apply a force to the rotor to decelerate the wheel’s rotation so that friction is increased between tires and road and the trailer slows/stops: this ability is described as the brake system’s BRAKE TORQUE.

  2. Be able to create enough friction between the pad and rotors to convert the trailer’s kinetic energy to heat; this is called CLAMPING FORCE; and be large and heavy enough (the rotors) to absorb that heat without damage; this is called THERMAL CAPACITY.