I was reading (I think) Frank Berto's "The Dancing Chain" book last weekend, and it mentioned some efficiency research that Berto did with 3-speed hubs, 7-speed hubs, and regular derailleur bikes. If I remember correctly, drivetrain energy loss was about 3-5% for derailleurs, and 5-7% for internally geared hubs.
More interesting than this was a statement that the highest losses on derailleur bikes came from 13-tooth cogs. The results implied that using a 13-tooth cog was tanamount to using a Sturmey Archer 3-speed hub. And Berto asserted that this is why 14-28 rear clusters are so popular on road bikes of the 1970's and 1980's.
Has anything changed ?
Are 13-tooth (and 12-tooth (and 11-tooth)) cogs only 90-92% efficient?
I was reading (I think) Frank Berto's "The Dancing Chain" book last weekend, and it mentioned some efficiency research that Berto did with 3-speed hubs, 7-speed hubs, and regular derailleur bikes. If I remember correctly, drivetrain energy loss was about 3-5% for derailleurs, and 5-7% for internally geared hubs.
More interesting than this was a statement that the highest losses on derailleur bikes came from 13-tooth cogs. The results implied that using a 13-tooth cog was tanamount to using a Sturmey Archer 3-speed hub. And Berto asserted that this is why 14-28 rear clusters are so popular on road bikes of the 1970's and 1980's.
Has anything changed ?
Are 13-tooth (and 12-tooth (and 11-tooth)) cogs only 90-92% efficient?
- Don Gillies San Diego, CA
There's an inherent relationship between cog size and mechanical drag, since the chain links have to rotate further on their pins the smaller the cog gets.
In actual usage, however, if you are in the 53-11 and pedaling at a decent cadence, the speed would be high enough so that the mechanical drag would be trivial compared to aerodynamic drag.
Good answer... but as i said before... if are not strong enough doesnt matter it will be less eficient hehehe... common sense right? :P
cya 🙂
Quoted message said:
There's an inherent relationship between cog size and mechanical drag, since the chain links have to rotate further on their pins the smaller the cog gets.
In actual usage, however, if you are in the 53-11 and pedaling at a decent cadence, the speed would be high enough so that the mechanical drag would be trivial compared to aerodynamic drag.
