Drum & Disc Brake Tech - Whoa, Whoa, Whoa! Photo Gallery
The master cylinder provides fluid pressure to each wheel. Disassembled from this master are the primary and secondary pistons. As you step on the brake pedal, the primary piston moves forward in the bore and fluid pressure builds. Next, the pressure between the primary and secondary pistons forces the secondary piston to compress the fluid in its circuit. Finally, all the pressure is transferred to each brake to slow or stop the vehicle.