The clutch assembly fitted to early Mini models was of BLMC manufacture. It was of the single dry plate, coil spring type. In 1964, an improved Borg and Beck diaphragm type clutch was introduced. Both types of clutches are unusual because there are major parts of the clutch assembly on both sides of the flywheel.
The main parts of the clutch assembly on the outside of the flywheel are the spring housing, the thrust plate, the release bearing, the coil pressure springs (or diaphgram on later models) and the three driving straps.
Located on the inside of the flywheel are the clutch disc and the pressure plate. The spring housing is firmly bolted to the pressure plate by 3 bolts and spring washers. The spring housing is held to the flywheel by driving straps which are held a little way away from the outer clutch face by spacing washers. The clutch disc is free to slide along the splines of the primary gear which is fitted to the end of the crankshaft. Friction lining material is riveted to the clutch disc which has a segmented hub to help absorb transmission shocks and to ensure a smooth take-off.
The clutch is actuated hydraulically. The pendant clutch pedal is connected to the clutch master cylinder and hydraulic fluid reservoir by a short pushrod. The master cylinder and hydraulic reservoir are mounted on the engine side of the bulkhead in front of the driver. Depressing the clutch pedal moves the piston in the master cylinder forwards, so forcing hydraulic fluid through the clutch hydraulic pipe to the slave cylinder. The piston in the slave cylinder moves forward, on the entry of the fluid and actuates the clutch operating lever by means of a short pushrod. The opposite end of the operating lever slots, by means of a balljoint, into a throwout plunger.
As the pivoted operating lever moves backwards, it bears against the release bearing, pushing it forwards. This in turn bears against the clutch thrust plate, the spring housing, and the pressure plate which all move forward slightly thus disengaging the pressure plate face from the clutch disc.
When the clutch pedal is released, the pressure plate springs force the pressure plate spring housing outwards, which, because it is attached to the pressure plate, brings the pressure plate into contact with the high friction linings on the clutch disc. At the same time the disc is forced firmly against the inner face of the flywheel and so the drive is taken up.
Although space is limited, removal of the clutch and flywheel assembly, for inspection or overhaul can be carried out with the engine and transmission assembly still in position in the car.