The figure shows the air gap, axial force, and de-clutching force dependent on the clutch displacement for a declutching process.
Considering equal displacements up to the formation of an air gap, the coil and diaphragm spring clutch have a similar characteristic of the axial force over the clutch displacement.
In the case of the diaphragm spring, the de-clutching force reaches a maximum. Thus the applied pedal force for coupling is limited and in the decoupled condition smaller than the steadily rising force of the coil spring clutch over clutch displacement. For complete de-clutching, an additional displacement between the linings (air gap) has to be adjusted. In the case of the coil spring clutch, it leads to a rise in the pedal force whereas the pedal force decreases in the case of the diaphragm spring clutch.
In addition, the varying spring characteristics decide the axial force which contributes towards clutch wear.