Abstract: A friction clutch for a motor vehicle comprises a cover plate and a pressure plate, with an elastic diaphragm between them. The diaphragm has an outer peripheral portion which is formed with two concentric annular ribs projecting axially and defining respective convexities which are oriented in opposite directions. Each of these convexities cooperates with a respective surface portion formed in facing relationship with the diaphragm on a corresponding one of the members comprising the pressure plate and the cover plate. The diaphragm having these ribs has a cross section, taken in an axial plane through the annular peripheral portion of the diaphragm, which is substantially in the form of a letter S or Z.