Road cars use a single piston attached to the brake pedal. This piston is then connected to all 4 wheels. This clearly works OK, but it has the limitation that you cannot adjust the braking front to rear independently. On tarmac it is possible to have the front brakes working very hard, and of course this is motorsport so you only brake one way, very hard. But under this hard braking the rear brakes tend to lock, causing the back of the car to become out of control. Conversely on gravel you cannot brake so hard, but also to get the car to turn faster you often want to lock the rear wheels so that you turn the car round on the brakes.

To achieve this cars involved in motorsport use seperate cylinders for the front and rear brakes. The size of these cylinders can also be changed. The cylinders are operated by two rods which are in turn connected to either end of a rod with a spherical bearing in the middle. As this bearing is moved one way or another inside it’s housing it put more force on the end it is closest to. Changing the piston is a much larger job, and generally only done when the system is installed. The smaller the piston diameter the higher the pressure that can be generated for the same pedal force.