Q Factor (Bicycles)

The Q factor of a bicycle is the distance (measured parallel to the bottom bracket axle) between the pedal attachment points on the crank arms. It may also be referred to as the "tread" of the crankset. cite web
url = http://www.sheldonbrown.com/bridgestone/1992/1992.pdf
title = The 1992 Bridgestone Bicycle Catalogue: It's 1992--Do You Know What Your Q Factor Is?
accessdate = 2008-05-29]

Q factor is a function of both the bottom bracket width (axle length) and the crank arms. Bottom brackets axles vary in length from 103mm and 127mm. MTB cranks are typically about 20mm wider than road cranks.cite web
url = http://www.recumbents.com/WISIL/qfactor/qfactor.htm
title = The Q-Factor
accessdate = 2007-02-25]

A wider tread will mean less cornering clearance for the same bottom bracket height and crank arm length.

A narrower tread is desirable on faired recumbent bicycles because then the fairing can also be narrower, hence smaller and lighter.

It is also claimed that a narrower tread is ergonomically superior because it more closely matches the nearly-inline track of human footsteps.cite web
url = http://www.sheldonbrown.com/gloss_tp-z.html#tread
title = Sheldon Brown's Bicycle Glossary
accessdate = 2007-02-25|last=Brown |first=Sheldon |authorlink=Sheldon Brown (bicycle mechanic) |publisher=Sheldon Brown]

Though it seems intuitive that a closer tread is superior, it must be remembered that a walking person must put their foot more to the centerline of the body to balance. This is not the case when pedaling a bicycle, where the "steps" are so very close together and balance a non-issue. some experts believe that to reduce torquing of the knee the q factor should be adjusted so that the foot tracks in line with the knee and hip. Fact|date=October 2007

References

See also

*Bicycle
*Bottom bracket
*Crankset