Clutch Discs

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. The clutch assembly 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 disc is the driven member and the component that connects the engine with the transmission and driveline and as such it receives the most wear. You can restore optimal clutch operation and performance with one of our OE quality replacement clutch discs.

A clutch disc has friction material similar to brake lining on both sides at its perimeter. This material contacts the flywheel face on one side and the clutch pressure plate’s pressure ring on the other. The friction material and the clamping force of the pressure plate allow the flywheel/disc/pressure plate 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 via hydraulic or mechanical linkage. The spring pulls 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.

Every time the clutch is disengaged and engaged, the clutch disc slows down and speeds up, a process that creates heat and wear. Nevertheless, a modern clutch disc is expected to withstand this heat and abuse and provide many thousands of miles of reliable service, all while engaging and disengaging smoothly. But even the best clutch discs will eventually wear out, and the friction material will become thin to the point where there isn’t enough to grip the flywheel and pressure plate, which results in slippage and poor performance. The friction material on a clutch disc can be organic, ceramic, Kevlar, or metallic. Organic material is the most common type used for original equipment and aftermarket OE replacement clutch discs, as it exhibits high strength and wear resistance while providing smooth engagement.

On a typical replacement clutch disc, a wavy flat piece of metal called a marcel is positioned between the friction material and the disc. The marcel acts as a spring, cushioning the engagement of the disc with the flywheel and pressure plate to ensure smooth operation without chatter. A clutch disc can be constructed with a solid or a sprung hub. On a sprung hub clutch disc there is a plate to which the friction material is attached and an outer plate and the two are riveted together, with the hub in between. From 4 to 8 coil springs are arranged in openings around the splined hub center and the springs are also captured by recesses in the friction plate and outer plate. With this construction the hub is actually driven by the disc via the springs. The springs absorb shock when the clutch disc is engaged with the faster spinning flywheel, ensuring smooth clutch operation without chatter, and they also dampen engine vibration. Sprung hub clutch discs are generally used with solid mass flywheels for street use, while rigid hub discs are used with DMFs (Dual Mass Flywheels) and for racing.

No matter what you’re working on, we have the replacement clutch disc and clutch components needed to restore proper clutch operation. We offer clutch discs and clutch components that are manufactured to original equipment specifications, so when repairs are completed you can count on the clutch performance your vehicle was designed to deliver. Although the clutch disc bears the brunt of clutch wear, all clutch components should be carefully examined during the repair process. At the very minimum the clutch pressure plate and release bearing should be replaced along with the disc. The pressure plate surface also wears, and the diaphragm spring can weaken over time from heat and extensive use. The release bearing also wears, particularly on vehicles used in stop-and-go traffic where the clutch pedal is depressed for long periods. The flywheel surface wears too, but the disc contact surface can be often be restored by machining the flywheel on a flywheel grinder. In addition to clutch discs, you’ll find clutch pressure plates, release bearings, flywheels, and more here on our digital shelves.