Disc Brake System: Description and Operation

HYDRAULIC PRESSURE APPLY
When the footbrake is applied, hydraulic pressure from the master cylinder (in the hydraulic assembly) pushes the brake caliper piston and, with it, the inboard brake pad on to the rotor/disc. The hydraulic body reacts and slides on the guide pins to bring the outboard pad into contact with the disc. The clamping force on both sides of the disc is then equal.

HYDRAULIC PRESSURE RELEASE
When hydraulic pressure is released, the piston seal retracts the piston a small amount. This allows the moving parts to relax sufficiently for the brake pads to remain in close proximity to the rotor/disc, ready for the next brake application.