The clutch is considered to be the drive train component which is subjected to the highest strain. The momentum which it has to transfer, depends first of all, on the available diameter and the engine torque to be transferred. Of course the pressure force of the springs, thus the pedal force, should also not be excessive. Finally, as a rule, a security factor of 1,1 to 1,6 - which has not yet been entered into the formula below - is taken into account.
The friction coefficient (dry) for organic pads or linings is 0,25 to 0,5, and for inorganic 0,3 - 0,6. In wet-clutches with different linings it is lower.