An improved rotor or stator split ring seal assembly includes a flexible ring-advancing mechanism that advances at least one of the split ring halves radially inward, so that during assembly the split ring halves meet before adjacent elastomeric members, thereby preventing the elastomeric members from expanding between the seal ring halves and interfering with their alignment. The ring-advancing mechanism is flexed as the seal is assembled, thereby allowing the ring halves to be seated in the housing. The ring-advancing mechanism can be removable after assembly or internal to the seal. In various embodiments, the ring-advancing mechanism is a flexible bracket, a coil spring, or a vertical or horizontal leaf spring. Separate, identical ring-advancing mechanisms can be included with each of the housing halves so as to advance the split ring halves symmetrically.