Disc Brake System: Description and Operation

Brake System
the braking system features disc brake and calipers on all four wheels. the hydraulic system has a dual circuit that is split diagonally. A brake booster is fitted to all models. the system incorporates Anti-Lock Brakes (ABS) as a standard with its sub systems of Electronic Brake Force Distribution (EBV), Cornering Brake Control (CBC) and Engine Torque Feedback Control (MSR).

Purpose of the System
the Brake System provides the stopping power for the MINI and a cable operated parking brake. System components include:

- Brake Booster
- Master Cylinder with Reservoir
- Front Wheel Brake Assemblies
- Rear Wheel Brake Assemblies
- Parking Brake

System Components

Brake Booster
All cars are fitted with a 10" diameter vacuum brake booster. the booster is vented through an aluminum baffle plate, fitted between the booster and the bulkhead.

Master Cylinder with Reservoir

the tandem master cylinder is available in two versions one for ABS/ASC and one for DSC, both have a piston diameter of 22.2 mm. the visible difference between the two units is the single sensor fitted to the underside of the master cylinder on the DSC unit. This sensor informs the DSC control unit whether the driver has applied the brakes during DSC intervention.

the reservoir is secured to the master cylinder by a bolt connecting two mounting tabs. A sensor monitors fluid level, and supplies information to the ABS/DSC control unit. Two "0" rings seal the unit to the master cylinder. the reservoir also supplies fluid to the clutch hydraulics on manual gearbox models. there is an integral filter in the filler neck to prevent dirt contamination of the fluid.

Front Wheel Brake Assembly




Internally vented discs of 275 mm diameter with single 48 mm piston floating calipers are used at the front. the brake hose is fixed to the caliper using a Banjo type bolt.

Rear Wheel Brake Assembly



Solid brake discs with a diameter of 260 mm and single 32 mm piston floating calipers are used at the rear. the pad on the inside is secured to the caliper piston via a spring that locates in a groove around the outside of the piston.

Principle of Operation
For normal brake operation, the brake booster assembly assists brake pedal pressure and the force is transmitted to the master cylinder assembly. the master cylinder assembly converts brake pedal movement to hydraulic pressure. Primary and secondary brake pipe circuits supply the hydraulic pressure via the ABS hydraulic unit to the brake calipers.

the primary circuit supplies the front right and rear left brakes while the secondary circuit supplies the front left and rear right brakes. the engine intake manifold provides the brake booster assembly with vacuum through a pipe and non-return valve.