Clutch Pressure Plates

The clutch allows the engine to be disconnected from the manual transmission when the vehicle is stopped and when the driver shifts gears. The clutch assembly consists of the flywheel, clutch disc, clutch pressure plate, and release bearing and is located within the bell housing, which mounts to the engine and supports the transmission. The flywheel is bolted to the engine’s crankshaft and the clutch pressure plate is bolted to the flywheel. The clutch disc is sandwiched between the flywheel and pressure plate and the splined center opening on the disc fits over the splined transmission input shaft.

The clutch pressure plate is the active member of the clutch assembly, providing the clamping force that holds the clutch disc against the flywheel when the clutch is engaged and the means to release the clutch disc and disconnect the engine from the transmission when the clutch is disengaged. Next to the clutch disc, the pressure plate receives the most wear in the clutch assembly. You can restore optimal clutch operation with one of our OE quality replacement clutch pressure plates or improve it with one of our performance units.

A clutch pressure plate consists of a heavy metal pressure ring that contacts the clutch disc friction material, a Belleville spring or a set of coil springs and 3 levers, depending on clutch design, and a sheet metal cover. The clamping force of the pressure plate along with the clutch disc friction material allow the flywheel/disc/pressure plate assembly to turn as one with the engine and transfer all the engine’s power to the transmission input shaft.

When the clutch pedal is depressed, the release bearing is forced against the pressure plate diaphragm spring or levers via hydraulic or mechanical linkage. The diaphragm spring or levers pull the pressure plate away from the clutch disc, thereby disconnecting the engine from the transmission. When the clutch pedal is released, the pressure plate begins to apply pressure to the disc, forcing it against the flywheel. As the disc’s friction material grips the flywheel and pressure plate, it begins to turn and at full engagement spins at engine speed, applying engine power to the transmission input shaft and driveline.

There are 3 types of clutch pressure plates, the diaphragm pressure plate, the Borg & Beck pressure plate, and the Long Style pressure plate. The latter 2 are sometimes referred to as “3 finger” pressure plates. The diaphragm clutch employs a cone-shaped diaphragm spring, also called a Belleville spring, which applies the clamping pressure for clutch engagement and release pressure for disengagement. Cuts in the cone portion create a number of fingers. When the clutch pedal is depressed and the release bearing exerts pressure on the fingers at the center of the spring, the spring flattens out and pivots over a fulcrum ring, pulling the pressure ring away from the clutch disc. When the clutch pedal is released, retracting the release bearing, the spring returns to its cone shape and the perimeter of the spring again forces the pressure ring against the clutch disc.

Both Borg & Beck and Long Style pressure plates have a number of small coil springs arranged over the pressure ring and 3 release levers, hence the 3 finger reference. The coil springs supply the clamping pressure for clutch engagement and the levers are mounted on pedestals. When the clutch pedal is depressed and the release bearing exerts pressure on the levers, they pivot and pull the pressure ring back, compressing the coil springs and releasing the clamping force on the clutch disc. When the clutch pedal is released, retracting the release bearing, the coil springs again force the pressure ring against the clutch disc. Diaphragm pressure plates require less pedal effort than 3 finger pressure plates, they provide smooth engagement, and are more suited to vehicles with cable operated or hydraulic clutch linkage, which is why they are the most common type of OE pressure plate. Borg & Beck pressure plates were used on older vehicles with mechanical, lever type, clutch linkage and Long Style pressure plates are used for racing.