Abstract: A friction clutch wherein the diaphragm spring is pivotably held between two seats one of which is provided at the inner side of the clutch cover and the other of which is secured to the cover by rivets or claws extending through slots between the radially inwardly extending prongs of the diaphragm spring. One side of the diaphragm spring has reinforcing ribs extending radially along the outer portions of the prongs, between the two seats and into the circumferentially complete outer marginal portion of the spring. That seat which is adjacent to the ribs has arcuate bridges which are slightly spaced apart from the ribs, and such seat is further formed with undulations which alternate with the bridges and define with the diaphragm spring shallow clearances to reduce the area of contact between the diaphragm spring and the respective seat. The bridges and the undulations reduce the danger of breakage of the diaphragm spring in the regions of enlarged outer end portions of the slots between the prongs.