The clutch is housed between the engine and transmission where it provides a mechanical coupling between the engine's flywheel and the transmission input shaft. The clutch is operated by a linkage that extends from the passenger compartment to the clutch housing. The purpose of the clutch is to disconnect the engine from the driven wheels when a vehicle is changing gears or being started from rest.

Disengaging the clutch separates the flywheel, the clutch plate and the pressure plate from each other. The flywheel is bolted to the end of the crankshaft and rotates with it. The clutch plate is splined to the gearbox in order for both to rotate together and the pressure plate clamps the clutch plate to the flywheel. When the pressure is released by depressing the clutch pedal, the crankshaft and gearbox input shaft rotate independently. When the foot is taken off they rotate as one.

The two primary types of pressure plate assemblies are coil spring assembly and one with a diaphragm spring.

In a coil spring clutch the pressure plate is backed by a number of coil springs and housed with them in a pressed-steel cover bolted to the flywheel. The springs push against the cover. Neither the driven plate nor the pressure plate is connected rigidly to the flywheel and both can move either towards it or away. When the clutch pedal is depressed a thrust pad riding on a carbon or ball thrust bearing is forced towards the flywheel. Levers pivoted so that they engage with the thrust pad at one end and the pressure plate at the other end pull the pressure plate back against its springs. This releases pressure on the driven plate disconnecting the gearbox from the engine.

Diaphragm spring pressure plate assemblies are widely used in most modern cars. The diaphragm spring is a single thin sheet of metal which yields when pressure is applied to it. When pressure is removed the metal springs back to its original shape. The centre portion of the diaphragm spring is slit into numerous fingers that act as release levers. When the clutch assembly rotates with the engine these weights are flung outwards by centrifugal forces and cause the levers to press against the pressure plate. During disengagement of the clutch the fingers are moved forward by the release bearing. The spring pivots over the fulcrum ring and its outer rim moves away from the flywheel. The retracting spring pulls the pressure plate away from the clutch plate thus disengaging the clutch.

When engaged the release bearing and the fingers of the diaphragm spring move towards the transmission. As the diaphragm pivots over the pivot ring its outer rim forces the pressure plate against the clutch disc so that the clutch plate is engaged to the flywheel.

The advantages of a diaphragm type pressure plate assembly are its compactness, lower weight, fewer moving parts, less effort to engage, reduces rotational imbalance by providing a balanced force around the pressure plate and less chances of clutch slippage.

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