A friction clutch mechanism includes a diaphragm spring, a pressure plate having a peripheral fulcrum acting against a first face of the diaphragm spring, and a pair of axially opposed intermediate fulcrums supported by a clutch cover and acting on the opposite faces of the diaphragm spring along a radially intermediate portion thereof. The friction clutch mechanism has an additional elastic element, operatively associated with a first intermediate fulcrum of the pair of axially opposed intermediate fulcrums, and axially and elastically compressible in response to a deflection of the diaphragm spring towards an open friction condition. The additional elastic element has a radially innermost annular portion resting on one or more bearing surfaces supported by the clutch cover, and a radially outermost annular portion that cantilevers and has a protrusion circumferentially extended and axially projecting towards the first face of the diaphragm spring to serve as the first intermediate fulcrum.