Necessity of brake: In an automobile, if the pressure from accelerator pedal is removed, the vehicle tends to slow up because of wind resistance, drag of engine and road friction. These forces, of course, would stop the vehicle but in present day traffic, this would be quite unpredictable and dangerous. The braking system provides added friction to overcome motion and to slow up or to stop the vehicle. The momentum or kinetic energy developed by the vehicle when in motion is converted to heat energy by the friction of brake shoes and drums which is dissipated into the surrounding air. Therefore the braking system is necessary to stop the vehicle or to retard the speed of vehicle within shortest interval of time with safety.