So you got a fast motorcycle? Try riding fast assuming your brakes don't work. You'll find it impossible. As much as brakes are there to control speed and stop your motorcycle, their effectiveness is required to ensure you can actually use all that performance in the first place.
The one common phenomenon that connects steering, acceleration and braking is friction. The braking system essentially causes deceleration by converting kinetic energy into heat using friction. It usually has three parts. The first is the actuator which is the human interface – usually in the form of a lever or a pedal.
Then comes the force multiplier. This is important because the amount of force needed to stop even a lightweight motorcycle is immense. Even the fittest, strongest person will find it hard to press a lever hard enough to produce reasonably good deceleration. The force multiplier takes the form of mechanical or hydraulic systems. Old and retro-styled motorcycles, use a simple mechanical system that you can see in the drum brake setup. IF you look close, you'll see a metal shaft that connects the brake cable to the drum brake. The length of the shaft multiplies the force generated by your squeezing the brake lever.
Hydraulic systems replaced mechanical systems because they proved far more efficient and eventually far more reliable and maintenance-free. In the same way as other hydraulic systems work, hydraulic braking systems also use two interconnected cylinders with in-compressible hydraulic fluid to multiply a small movement at the actuation and into a much larger force but a much smaller movement. The principle is called hydraulic force multiplication and you can see it working in everything from a hydraulic jack to almost every single disc brake on motorcycles.
So you pull the brake lever, or press the pedal and the force multiplier mechanism applies a strong force, then what happens? As we said, in every case, the brake uses friction as a process to convert kinetic energy into waste heat. The loss of energy causes a drop in speed, leading to what we usually call braking.