A method for making a rotor for an electric motor. An elastomeric ring loosely slides over a motor shaft and inside a flux ring. End plates are attached to the longitudinal ends of the flux ring so as to longitudinally compress the elastomeric ring which radially inwardly expands against the motor shaft and radially outwardly expands against the flux ring. In a modification, the flux ring has a smaller-diameter annular disk near each of its longitudinal ends, and each attaching end plate longitudinally compresses a longitudinally-shorter elastomeric ring against a corresponding smaller-diameter annular disk.