A shoulder ring, for installation in a threaded pipe coupling between the installed pin ends of two pipes being connected by the coupling, has opposing end faces and a central opening, and may be lobate or circular in shape. The shoulder ring provides enhanced axial retention within the coupling by incorporating a thread element which engages the internal threads of the coupling to prevent or deter displacement of the ring from the coupling. Alternatively, enhanced axial retention may be provided by means of an interference or interlocking fit that is plastically induced during the ring installation process. The shoulder ring may be of lobate or circular configuration, with the axial retention of lobate embodiments being further enhanced by forces acting radially outward against the coupling due to elastic deformation of the ring during installation. Also disclosed are tools for installing the shoulder rings in a threaded coupling.