21.11 Bushing fatigue failure

Bushing fatigue failure occurs as the result of service overloads. The crack originates at a point on the inside surface of the bushing and progresses longitudinally or circumferentially until it cracks entirely with traumatic component failure. Failures can also be caused by incorrect sprocket selection or manufacture.
This condition can be remedied by eliminating overloads, increasing sprocket sizes, changing sprockets which are in a bad condition or an incorrect form, notably where the root diameter is oversized and causing the chain to bottom out.