A bearing assembly (A-H) enables one member (4) to rotate relative to another member (2) about an axis (X). It includes a bearing (6) having an inner race (54) on one of the members, an outer race (74, 126, 164, 250) in the other member, and rolling elements (58) between raceways on the two races. A seal (10, 180, 210, 256) excludes contaminants from the interior of the bearing, and it includes a wear ring (92, 184, 214, 276) carried by an extension (80, 128, 144, 168, 252) on the outer race beyond the raceway of that race, a contacting wear ring (90, 182, 212, 278) carried by the member on which the inner race is located or else by a can (110, 230, 254) that is fitted to the inner race. The seal also includes backing elements (94, 96, 192, 194, 216, 218, 294) for supporting the wear rings on that which carries them, and in most instances the backing elements exert a biasing force on the wear rings to maintain them in contact, so that they establish a dynamic fluid barrier. The backing elements may include O-rings (94,96), polymer connecting segments (200) or springs (292) and a membrane (294).