Chainline is the angle of a bicycle chain relative to the centerline of the bike's frame. A bicycle is said to have perfect chainline if the chain is parallel to the  frame, which means that the rear sprocket is directly behind the front sprocket . Chainline also refers to the distance between a sprocket and the centerline of the bike . Bicycles with straighter chainline are more efficient due to the frictional losses incurred by running the chain straight around both sprockets but at an angle between them . This is the main reason that a single-speed bicycle is more efficient than a derailleur geared bicycle which is shifted into an identical gear combination . Single-speed bicycles must have the straightest possible chainline in order to prevent the chain from falling off. This is particularly important for fixed-gear bicycles, because chain derailment can cause such a bike's rear wheel to lock. See also Bicycle gearing
Chainline is the angle of a bicycle chain relative to the centerline of the bicycle frame. 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 . 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 . 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 . See also Bicycle gearing
R
bike's
bicycle
A
centerline of the
R
sprocket
chainring
R
bike
frame
R
with straighter chainline are more
without a straight chainline are slightly less
D
the
D
straight around both sprockets but
R
them
the front chainring and rear sprocket
R
is
can be
D
which is shifted into an identical gear combination
R
must
should
R
in order to prevent the chain from falling off. This is particularly important for fixed-gear bicycles, because chain derailment can cause such a bike's rear wheel to lock.
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