A mechanical system with a one-way clutch, such as a motor vehicle alternator pulley, includes an outer first ring and an inner second ring able to move relative to one another in rotation about a central axis and delimit between them, radially with respect to this central axis, an annular housing. The mechanical system includes a free-wheel mechanism having members arranged in the annular housing, and at least one rolling bearing providing rollers arranged in the annular housing. The first and second rings are common to the free-wheel mechanism and to the rolling bearing. The members of the free-wheel mechanism are cams in contact with a first race formed by the first ring and a second race formed by the second ring. The first and second races are circular, centered on the axis of rotation and have no ramp.