Low molecular weight, high Tg resins, with applications including tire additives and adhesives. An oligomer is obtained by ring opening metathesis polymerization (ROMP) of a sterically encumbered cyclic monomer with an olefinic chain transfer agent. The sterically encumbered cyclic monomer and the olefinic chain transfer agent are present in the polymerization at a molar ratio of from 2:1 to about 40:1. Also, methods for making the oligomer by ROMP.