In a flywheel mechanism of the axially expanding type a clutch plate which is rotatable with a shaft and from which the mechanism is driven, is provided on pitch circles of greater and smaller diameters with outer and inner clutch faces with which complementary clutch faces on the mechanism are alternately engageable. This defines first and second clutch engagements of higher and lower torque settings which are operative, respectively, when the flywheel mechanism is in an inoperative brake-applying position and when the flywheel mechanism is in an operative brake-applying expanded position.