A disk clutch is used in a vehicle's manual transmission and is sandwiched between the flywheel and the pressure plate. In some high-performance applications, a multiple disk clutch is used to better harness the high amounts of horsepower and torque produced by the engine. This device can be made up of organic materials, metal and iron compounds, and even Kevlar in high-performance applications.
Many factors go into determining the proper disk clutch set up far a vehicle including engine size and power output, vehicle weight, vehicle use and even tire size. Any time a new one is placed in a vehicle, its flywheel should be resurfaced. The purpose of resurfacing the flywheel is not only to ensure that a flat and smooth surface exists for the new clutch disk to operate against, but also to be certain there are fresh machine markings on the flywheel to assist the new disk in wearing in evenly.
On multiple disk clutch applications, it is often necessary to replace the steel disks that ride between the clutch disks. These steel disks frequently become burned and warped from the high heat generated by a slipping clutch. The pressure plate should also be changed or machined when installing a new disk clutch assembly. Many high-performance pressure plates have the ability to adjust the way in which the plate engages the disk. On road driven vehicles, the pressure plate is merely bolted in place with no adjustment required.
On street driven clutch applications, the clutch is equipped with springs around the perimeter of the disk. These springs allow the disk to absorb some of the shock of releasing the clutch, thereby reducing or eliminating clutch chatter. Clutch chatter is a violent shaking that has been know to break drive shaft joints, engine and transmission mounts and has even caused windshields to crack and break in extreme cases.
In high-performance, race-only vehicles, disk clutch assemblies have no springs and consist of a solid steel plate. This allows the clutch to engage much stiffer and with less slippage. Eliminating clutch slippage results in the vehicle moving forward a fraction of a second sooner. In racing applications, seconds add up and even a fraction of a second could be the difference between winning or losing a race. The disk clutch is one of the most important links between the engine and the drive line.