An earth boring bit has a bit body having a depending bearing pin. A cone has a cavity rotatably mounted on the bearing pin. A seal groove is formed in the cavity of the cone. An elastomeric seal ring is located within the groove and forms a seal between a base of the groove and the bearing pin. The seal ring has two side surfaces, each spaced from one of the side walls of the groove by a clearance. Elastomeric protuberances protrude from each of the side surfaces of the seal ring for non-sealing contact with one of the side walls of the groove.