Raceway

The raceway is the hardened, precision-finished surface on the inner and outer ring (or shaft and housing washer of thrust bearings) on which the rolling elements run. In ball bearings it is a groove whose radius is slightly larger than the ball radius (osculation); in roller bearings it is cylindrical, tapered or spherical. Contact areas are small, so Hertzian pressures are high. Surface finish and form accuracy govern running noise, friction and the elastohydrodynamic lubricant film. The raceway is also the primary damage zone: rolling contact fatigue, false brinelling and electrical fluting all appear here, and indented contamination particles act as fatigue initiators.