Braking system is similar in both scooters and bikes.there are two commonly used brake system . A mechanical or hydraulic brake is used in motor cycles.Braking action is caused due to Frictional force between the contacting surfaces.And later this energy is converted into heat energy.
Further some bikes use Drum brakes while some bikes use Disc brake.
Drum brakes are simpler and efficient method used for braking. most drum brakes are mechanical actuated
The above diagram shows a hydraulic actuated drum brakes. the working is simple. when hydraulic fluid is forced inside the cylinder ,the piston pushes the which in turn pushes the brake shoes against the rotating drum.braking force is due to friction between the shoes and the drum. The drum is directly attached to the wheel.
Above image shows the mechanical link to actuate a drum brake (rear wheel), THe working is very simple and slef explanatory after seeing the video below.
If it is a mechanical actuated brake the piston is replaced by a S cam.
Disc brakes are hydraulic actuated brake. Before entering into into Disc brakes its required to know about Hydraulic brakes.
The working is effected by basic laws called as Pascals law and hydro static laws .
The main component of hydraulic brake is the master cylinder . A master cylinder working is similar to squeezing tooth paste.
A master cylinder acts like heart of the brake pumping braking fluid to to all chambers under pressure.
The red color rod is attached with brake handle, when this is pressed the hydrualic fluid is squeezed and actuates the piston.
Here is the position of master cylinder of bike.
When the pedal is pressed , the hydraulic fluid is forced to flow out from mater cylinder ,this forces the piston in caliper to expand and squeezes the rotor and wheels get retarded.