Thursday, 6 March 2014

Hub Gear Efficiency vs Derailleur Gear Efficiency


Hub Gear Efficiency vs Dérailleur Gear Efficiency - Intro 

If like me you spend hours awake at night worried about the comparative efficiencies of Dérailleur and Hub gears then I hope this post will help restore your normal sleep patterns.

Hub Gear Efficiency vs Dérailleur Gear Efficiency - Findings

The first study compares a great many gear hub types with a Shimano 27 speed dérailleur setup.  There are three sets of results for each gear system, this is because each system was tested under 3 different loads, to simulate different pedal pressure.




Summary of Findings









The abovegraph shows the above melded in to an all manufacturer average, and shows that on average over the entire range of gears that 3 speed hubs and Derailleur gears are of equal efficiency whilst hubs with more gears have slightly lower efficiencies.

So what of Rohloff . I have left them out. The above paper was written before rolhoff released there later paper, which focusses almost entirely on the efficiency of their hub, it is also written by rolhoff, so I can not see its value. The above study put rolhoff hub gear efficiency at 90.9% whilst Rohloff claim 96.7%.


The studies quoted in this post are from the Technical Journal of the IHPVA;

Efficiency Measurements of Bicycle Transmissions -a neverending Story?
by Bernhard Rohloff and Peter Greb (translated by Thomas Siemann)

and

The mechanical efficiency of bicycle derailleur and hub-gear transmissions.

 Chester R. Kyle, Ph.D.

Frank Berto

Hub Gear Efficiency vs Derailleur Gear Efficiency - Conclusion

For the average cyclist who is not in a race a  4% drop in efficiency will not be a problem, but for a 100 mile bike race you might want to stick with Dérailleur gears, unless the race is very flat then a 3 speed might be applicable. For most though a hub gears lack of maintenance is the draw factor, and within the context of utility cycling this install and forget aspect is more important than the hub gear efficiency losses.

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