Relative Efficiency of Various Bike Transmission Systems

[Alaskan]

In researching whether or not to go for a Nuvinci continuous drive transmission, I was looking to find out what the cost is in terms of efficiency loss versus the more common derailleur/gear cassette system. I found this fascinating study on wattage loss between where the foot meets the pedal and where the tire meets the road. Test rides of two bikes with the Bosch CX drive, one with an 11 speed traditional setup and the other with a belt driven Nuvinci seemed to line up and support the accuracy of the findings in the article. I chose to get a Riese & Muller Nevo Nuvinci GH, knowing that I would be giving up about 10% efficiency in favor of low maintenance, quiet operation, durability and that hard to pin down coolness factor.

This should be required reading for anyone trying to decide what transmission system is best for them.

https://www.cyclingabout.com/speed-difference-testing-gearbox-systems/

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The Results
While the data from the graph indicates the drivetrain efficiency for each gear, I’ve averaged out the drivetrain efficiency across each gear range to come up with the following numbers:

Singlespeed: 97% efficient (Drivetrain loss of 6w @ 200w).
Rohloff : 94.5% efficient on average across 14 gears (Drivetrain loss of 11w @ 200w)
Pinion: 90.5% efficient on average across 18 gears (Drivetrain loss of 19w @ 200w).
Shimano Alfine 11: 90.5% efficient on average across 11 gears (Drivetrain loss of 19w @ 200w).
Shimano Nexus 8: 90% efficient on average across 8 gears (Drivetrain loss of 20w @ 200w).
Nuvinci 360: 83.5% efficient on average across the gear range (Drivetrain loss of 33w @ 200w)."

 

[JRA]

Di2 Alfine 11 works for me. Because I have vertical dropouts I need to use a chain tensioner which cuts into the efficiency some. A little spendy but I don't mind shifting and as far as coolness factor goes.......

Powerloss through the drivetrain adds up over time. An e bike does a good job of compensating as long as you have the proper gear range for your riding terrain and style. Not only when under power but when you stop pedaling an internal gear hub can still have parasitic drag and this it the powerloss that saps your legs when riding without power, along with the overall weight of the bike of course.

But in the end it is hard to beat a cassette/derailleur system for efficiency given that it is tune. Also a lot lighter weight, didn't weigh my Alfine but certainly the bike is heavier with it but the performance meets my needs and is still under 50lbs without any lightweight components otherwise.