Clutch: Description and Operation

Clutch

There are two types of clutch assemblies used on the MINI. The MINI COOPER uses a conventional type clutch and flywheel arrangement, the MINI COOPER S has an upgraded clutch in combination with a dual mass flywheel.

The MINI COOPER S has an upgraded clutch assembly with a dual mass flywheel. Primary components of the COOPER S clutch system include:

- Model Specific Pressure Plate.
- Model Specific Clutch Disc.
- Dual Mass Flywheel.
- Clutch Release Bearing.
- Clutch Hydraulic System.

System Components

Pressure Plate

The MINI COOPER S uses a diaphragm type pressure plate, constructed from steel housing 18 spring steel fingers. The clutch is located on the flywheel by three dowels and is retained by 6 external torx head bolts.

Clutch Disc
The clutch disc on the MINI COOPER S is constructed from cast iron and has no damper springs fitted, with a friction surface on each side. The torsional forces are absorbed by the dual mass flywheel. The disc diameter is 216 mm and has a protruding spline center boss that is installed away from the flywheel.

Dual Mass Flywheel
The MINI COOPER S is fitted with a dual mass flywheel that is attached to the crankshaft by 8 bolts. The flywheel is correctly aligned when the crankshaft center dot is aligned with the scalloped recess on the flywheel. A ring gear is fitted on the outer 'primary' part of the flywheel, and will not be available separately in service.


The dual mass flywheel is used to insulate the gearbox from torsional and transient vibrations produced by the engine or driveline. The flywheel consists of a primary and a secondary flywheel. The drive between the two is transferred by a torsional damper made up of four coil springs located in the inside diameter of the primary flywheel. Two of the springs are of smaller diameter and fit inside the larger diameter springs.

The two pairs of coil springs are located in a recess in the flywheel, between two riveted retainers. A roller bearing is pressed onto the central boss of the primary flywheel and is retained with a riveted plate. The bearing provides the mounting for the secondary flywheel. The secondary flywheel consists of two parts, an outer flywheel, which provides the friction surface for the clutch drive plate, and an inner drive plate, which transfers the drive from the primary flywheel via the coil springs, to the outer flywheel. The two components of the secondary flywheel are secured to each other with rivets.

The inner drive plate is located between the two pairs of coil springs and can rotate on the ball bearing in either direction against the combined compression force of the four coil springs. Under high torque loading conditions the secondary flywheel can rotate in either direction up to 70 degrees in relation to the primary flywheel.

Clutch Release Bearing and Hydraulics
The Clutch Release Bearing and Hydraulics is similar to that of the MINI COOPER. The Clutch Slave Cylinder is mounted towards the bottom of the transmission facing forward.