Chainline

The chainline is the angle of a bicycle chain relative to the centerline of the bicycle frame.^[1] A bicycle is said to have a perfect chainline if the chain is parallel to the centerline of the frame, which means that the rear sprocket is directly behind the front chainring.^[1] Chainline can also refer to the distance between a sprocket and the centerline of the frame.

Chainline on a fixed-gear bicycle

Bicycles without a straight chainline are slightly less efficient due to frictional losses incurred by running the chain at an angle between the front chainring and rear sprocket.^[1] This is the main reason that a single-speed bicycle can be more efficient than a derailleur geared bicycle. Single-speed bicycles should have the straightest possible chainline.^[2]

See also

• Bicycle gearing
• Bicycle performance