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> A stock Dura Ace drivetrain returned about 97-percent efficiency. Does anybody know the numbers of efficiency in fixie and single speed bicycles? I reckon th

by bigato 8y ago

> A stock Dura Ace drivetrain returned about 97-percent efficiency. Does anybody know the numbers of efficiency in fixie and single speed bicycles? I reckon they should be better given the absence of a derailler? I tried to search for it, but couldn't find numbers.

21 8y ago
Another article on this technology stated that the efficiency gain comes from there being only 4 points under load versus 8 points in a chain with derailleur system. A fixie also has only 4 points, since the derailleur is gone, so it's presumably more efficient. But the big problem is that there is also an efficient human cadence (I think around 100 RPM), and a fixie has a massive problem here. So overall, a fixie is massively more inefficient. Which I guess is no surprise, cycling competitions are run with geared bikes, not with fixies.
- bennyelv 8y ago
  This doesn't sound correct to me - the derailleur is on the "slack" side of the chain so is never under significant load. The only load is that required to pull the chain back from the crankset under enough tension to stop it from drooping, which is provided by the spring in the derailleur cage. All the load in the chain system is between the cassette and the chainrings on the top. Perhaps a link to the article will reveal more? There's a lot of BS in bike technology, so I'm automatically sceptical!
  - 21 8y ago
    Maybe load was not the appropriate word to use. Smith explains that that friction in a chain-based drivetrain is created largely at the eights points of articulation, where the chain bends around the chain ring, cassette and pulleys. "Any time a chain articulates, friction is created. And any time it disengages, friction is created," Smith said. "When you think about pedaling 95rpm, you are looking at 40,000 stiction points a minute." In the DrivEn system, those eight points are replaced by four points, each of which rotate on ceramic bearings. The chain ring's teeth and cassette's cog engage with the bearings on the shaft, which itself spins on bearings. https://www.bikeradar.com/road/news/article/ceramicspeed-driven-drive-shaft-52587/ https://www.bikeradar.com/road/news/article/ceramicspeed-dri...
danburbridge 8y ago
98-99% iirc for a fixed (track) gear setup. There has also been a recent trend on the track towards larger chainrings and sprockets for a slight increase in efficiency, as the chain has to go through less of a tight radius, whilst still maintaining the same gear ratio.

by bigato 8y ago

21 8y ago

Another article on this technology stated that the efficiency gain comes from there being only 4 points under load versus 8 points in a chain with derailleur system. A fixie also has only 4 points, since the derailleur is gone, so it's presumably more efficient. But the big problem is that there is also an efficient human cadence (I think around 100 RPM), and a fixie has a massive problem here. So overall, a fixie is massively more inefficient. Which I guess is no surprise, cycling competitions are run with geared bikes, not with fixies.

bennyelv 8y ago
This doesn't sound correct to me - the derailleur is on the "slack" side of the chain so is never under significant load. The only load is that required to pull the chain back from the crankset under enough tension to stop it from drooping, which is provided by the spring in the derailleur cage. All the load in the chain system is between the cassette and the chainrings on the top. Perhaps a link to the article will reveal more? There's a lot of BS in bike technology, so I'm automatically sceptical!
- 21 8y ago
  Maybe load was not the appropriate word to use. Smith explains that that friction in a chain-based drivetrain is created largely at the eights points of articulation, where the chain bends around the chain ring, cassette and pulleys. "Any time a chain articulates, friction is created. And any time it disengages, friction is created," Smith said. "When you think about pedaling 95rpm, you are looking at 40,000 stiction points a minute." In the DrivEn system, those eight points are replaced by four points, each of which rotate on ceramic bearings. The chain ring's teeth and cassette's cog engage with the bearings on the shaft, which itself spins on bearings. https://www.bikeradar.com/road/news/article/ceramicspeed-driven-drive-shaft-52587/ https://www.bikeradar.com/road/news/article/ceramicspeed-dri...

danburbridge 8y ago

98-99% iirc for a fixed (track) gear setup. There has also been a recent trend on the track towards larger chainrings and sprockets for a slight increase in efficiency, as the chain has to go through less of a tight radius, whilst still maintaining the same gear ratio.