The Basics of Brakes put simply – BRAKES MAKE HEAT!!
To accelerate your car, you burn fuel and the heat energy accelerates
the mass of the vehicle. Brakes reverse that process. By applying your
brakes, you are converting kinetic energy into heat, pure and simple, a
straight thermodynamic conversion. The amount of heat to be
absorbed (and therefore dissipated) by the brakes is a function of the
velocity of the car, the amount it weighs and the rate of deceleration.
Acceleration/Deceleration are mathematically “square functions”,
meaning to stop twice as hard takes four times as much effort,
generates four times as much heat and wears out the brakes four times
as quickly. Stopping four times as hard requires 16 times and so on.
It therefore follows that a big heavy vehicle stopping quickly from high
speed requires large heat absorbing capability and the ability to
dissipate that heat to the atmosphere.
Brake Pads and Disc Rotors make the heat that stops
the car
Brake Pads are manufactured from fibres, metals and binders chosen
for their friction properties. Essentially, all heat the pads generate has to
be passed into the disc rotor. The pad itself has to be able to handle
the extreme heat generated but it is not expected to do much towards
dissipating the heat, as its all done by the disc rotor.
A larger pad surface area is required for reducing the specific heat
load; a very small pad would become extremely hot, even if running
against a large rotor. It therefore follows that the key to stopping a
heavy car is good ability to absorb and then dissipate heat before
being called upon to do it all again. If the system is not sufficiently
cooled, fade will occur. The type and quality of the cast iron, the
design of the internal cooling vents and the surface friction
characteristics of the rotor all have an influence.