Types of Clutch

Here is some basic information about how a clutch works, links to videos of interest, and definitions of various components.

If you are looking for more general information on clutches, please have a look on the internet.

If you would like to see pictures of our racing products, please go to our Racing Clutch page and each part will have a photograph along with a description.

Dictionary of terms:

A Clutch:

A device to connect/disconnect the engine from the transmission to facilitate gear changes, which is required to match road speed to engine speed. 
Below is a very quick video on how a clutch works:

             

Uprated Road Clutch:

Also known as Group 'N' clutches, the clutch cover assembly is made from a sheet of pressed steel, it is a large diameter to give a better pedal feel and make the clutch long lasting, whilst still having a good torque capacity. They have uprated internals compared to standard components in order to make them more suitable for competition use and they are usually interchangeable with O.E.M. components. 

Clutch Cover Assembly: Its job is to hold the diaphragm spring and pressure plate in place and the release bearing actuates against it.

Clutch Diaphragm Spring: The component that provides the clamping load to the clutch internal parts so that the clutch does not slip when torque is applied. A diaphragm spring essentially works in the same way as a conventional coil spring, however can exert a far larger pressure over a short distance.

Pressure plate: The component in the clutch cover that the diaphragm spring presses against, the pressure plate then clamps against the driven plate when the pedal is released to allow the drive to be transmitted to the gearbox. They are usually manufactured from cast iron. 

Racing Clutch:

Also known as Group 'A' clutches, these use multiple plates, on a small diameter, in order to keep mass central to its axis of rotation, the outside of the clutch is usually made from a lightweight aluminium alloy. It is designed to have a high torque capacity, however at the expensive of comfort and driveability. 

Clutch Intermediate plate: Only used on multi-plate clutches, it is a large metal spacer separating the clutch discs. Provides additional friction surfaces to multiply the torque capacity of the clutch.


Flywheel:

Bolted to the crankshaft of the engine, it is designed to locate the clutch cover and it has a mounting surface for the driven plate to sit against. Around the circumference of the flywheel are teeth for the starter motor to engage in order to start the engine. 


A flywheel is used in order to give the engine inertia and momentum. However, for motorsport applications the flywheel is usually very lightweight so that the engine can respond quickly. 

Driven Plate or Clutch Disc:

The component with the friction material on it, mounted to the transmission input shaft via a spline system. Please look to our Road or Race Clutch page for part number prefixes and descriptions of the different plates available, this includes the list of gearbox splines which we stock. 

Organic clutch plates:-
The material on it is called "Organic facing" These can be made with or without 6 little springs in the centre.
We can supply these in a range of sizes from 140 to 240mm diameter. This type of clutch is the least aggressive to drive and the longest lasting, so ideal for use on public roads. 

Cerametallic Paddle plates:-
The bottom photo is of a 6 "paddle driven plate". These also come in a variety of sizes, with the option of 3 to 6 paddles, with sprung or ridged centres. 

These are used in a range of race, modified road, track-day, rally and general motorsport competition. 
Unpleasant to drive on the road, so not recommended, however, they have higher torque capacity than an organic clutch.  

Sintered Discs:-
Are only manufactured in 140 and 184mm multi-plate race clutches and are only available with ridged hubs. They are the lightest and also have the highest torque capacity, but are very aggressive to drive and not suitable for use on public roads. 
They will wear out very quickly if the driver does attempt to drive them progressively. 



Clutch Release Bearing:

The clutch release bearing operates against the fingers on the clutch spring in order to connect/disconnect the engine from the transmission. The bearing is controlled by the driver operating the clutch pedal via a cable or hydraulic setup.

Hydraulic Release Bearing:

The concentric hydraulic slave cylinder is a very efficient method of actuating the clutch. Using a hydraulic system reduces driver pedal effort, whilst increasing the control and consistency of the clutch. Light weight and space effective it considered the most reliable and system for motor sport.

Inertia:

Intertia is the tendency of a rotating object, such as a clutch and flywheel assembly, to resist changes in speed. Power is required to overcome this resistance to change speed. Low inertia components accelerate/decelerate more quickly than high inertia components resulting in quicker engine response and improved performance.

Torque:

Torque is the amount of twisting power provided by the engine. The clutch must be able to transmit the torque generated by the engine, plus an amount of inertia torque, without slipping.

Gearbox spline:

This is the shaft which comes out the front of the gearbox which the drive plate sits on. The drive plate should fit onto the shaft without any movement or ‘play’. Spline sizes are usually given as the outside diameter in mm or inches followed by the number of teeth, for example: 23.52mm x 24 Teeth. (1" x 23T)
We manufacture all of our own splines within the factory, as a result, driven plates can be made to order.


 

More technical information on clutch kits