Tuned rubber/viscous torsional vibration damper assemblies of the kind having a supporting rotor disk mounting an inertia mass coupled to the disk by viscous damping medium and elastic tuning spring, spacing and sealing rubber rings located in rubber ring accommodating grooves. A viscous damping medium working chamber is defined within the inertia mass radially outwardly about the rings. The rubber rings are molded and vulcanized in situ in said grooves and to the rotor disk and the inertia mass. The dampers may be provided with rubber spacer and bumper fingers extending from the rubber rings into the working chamber of the damper. The rubber rings may also be keyed to the inertia mass by means of integral lugs extending into socket apertures in the inertia mass. The dampers may be coated with a rubber skin on outside areas, the skin being connected to exposed areas of the rubber rings.