Chainline
From Infogalactic: the planetary knowledge core
File:Chainline (3621138368).jpg
Chainline on a fixed-gear bicycle
Chainline is the angle of a bicycle chain relative to the centerline of the bicycle frame.[1] A bicycle is said to have 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 also refers to the distance between a sprocket and the centerline of the frame.
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]
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