Rib, flange

A rib (flange) is a raised shoulder beside a raceway that guides the rolling elements axially and, depending on the design, carries axial load. In cylindrical roller bearings the rib layout defines the type: NU (two outer-ring ribs, ribless inner ring — axially free, ideal as floating bearing), N (reversed), NJ (one inner-ring rib, axial location in one direction), NUP (loose rib washer, both directions). Tapered roller bearings support their rollers on the large inner-ring rib. Roller-end/rib contact is sliding, not rolling: it limits permissible axial load, demands adequate lubricant viscosity, and fails first by smearing under starvation or axial overload.