- Biopace
Biopace is a
tradename of a type ofovoid bicycle chain ring that was intended to help overcome the "dead zone" where the crank arms are vertical and riders have littlemechanical advantage . Biopace was made and licensed byShimano .cite web
url = http://sheldonbrown.com/biopace.html
title = Sheldon Brown: Biopace
accessdate = 2008-05-25]The intention of most oval style chainrings is that at top and bottom dead centre (TDC and BDC) the effective diameter of the chainring was small, thus making the crank easier for the rider to turn through BDC for a constant chain tension. By having the chainring at its peak effective diameter with the cranks level, that is, where the rider has maximum leverage over the crank during the power stroke, better use can be made of the rider's power output.
Biopace chainrings do almost exactly the opposite to this, having the reduced chainring diameter coinciding with the cranks being horizontal. The reason this is beneficial is that it tends to smooth the pedalling action, allowing the rider's feet to carry a lot of momentum through the power stroke, having it smoothly removed at the bottom of the stroke rather than encouraging riders to push bigger gears and risk knee damage due to higher knee joint loadings. [cite web
url = http://www.rotorcranksusa.com/frequentquestions.shtml#q1
title = Rotor Cranks FAQ: How are Q-Rings different than other non-round rings such as Biopace
accessdate = 2008_05_25]Biopace chainrings are often cited as the epitome of a solution looking for a problem among the biking press, though there is little evidence to suggest they were particularly bad, just unnecessary. Problems with using these chainrings with a front derailleur may well have been the final nail in the coffin for biopace.
See also
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Crankset References
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