A method of forming a rotor for a positive displacement motor. The method includes forming a liner that includes at least two resilient layers and at least one fiber layer, and the at least two resilient layers are positioned so as to enclose the at least one fiber layer. The liner is positioned on a rotor tube, and the rotor tube includes a shaped outer surface including at least two radially outwardly projecting lobes extending helically along a selected length of the rotor tube. The liner is cured on the rotor tube so that the liner conforms to the radially outwardly projecting lobes formed on the outer surface and to the helical shape of the outer surface. The curing forms a bond between the liner and the outer surface and between the at least two resilient layers and the at least one fiber layer.