Next to your tyres these are probably the most important system on the car. For a braking system to work properly all the elements in the brakes must work effectively. There is nothing so heart stopping as a brake peddle that goes to the floor as you approach a junction !!
What are brakes ?
Very simple a brake is a mechanical device that can convert kinetic (energy of motion) energy into heat energy. The more effectively it does this the better the brakes will perform.
What do we need for good brakes ?
A rotating mass (The brake disc or drum)
A high friction pad, block or shoe
A means of bringing them both together smoothly and quickly when you apply the brake? (A Caliper or Wheel cylinder).
These components are well designed but even so take a tremendous amount of force when used and inevitably wear out after a certain number of miles. The life of the brake depends on,
How you drive
How heavy the vehicle is loaded
How you brake.
In order to apply the large forces necessary to bring the friction material and the discs together whilst not requiring people to be super strong a hydraulic system with a servo assistance is employed to ensure that your intentions are transferred to the braking system.
HEAT THE BRAKE KILLER
A typical family car slowing from 70mph to 40mph will cause the brakes to increase in temperature by over 25°C. The brakes will cool again but not as quick as they heated up. Rapid use of brakes on a twisty country road from high speed will soon cause the brakes to reach temperatures in excess of 200°C in the caliper and several hundred degrees on the surface of the disc. In the caliper the heat is absorbed by the mass of the caliper and the brake fluid. If the brake fluid is not within specification it may boil causing brake fade and or brake failure. At the disc's stresses are introduced to the disc at highpoints on the disc. The rapid heating and cooling of the disc can induce brake thinning, or warping leading to judder and poor contact between the disc and pad. This leads to reduced brake performance.
The sections that follow expalin in more detail the importance of brake fluid, brake lubricants and what is brake squeal.