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Bicycle Repair/Upgrading 10 speed to 21 speeed


Scott wrote at 2013-03-17 20:04:17
Isn't this a common misconception regarding the nomenclature of "10-speed?" In common speak this refers to the total number of gears. In math speak, I think this would be the total number of elements in both sets (front and rear). 21 is the number of gear combinations, 3 in the front derailleur system and 7 in the rear derailleur system (3*7=21). So, you already have a "21 speed" by your definition. Incidentally, 21 linear equations relating cadence (RPM) to angular velocity of the tire (MPH).  

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Sheldon Brown


I am a bicycle mechanic, educator and journalist.I can provide technical help with most types of bicycles.I`m also quite experienced as a Webmaster and photographer. Please don't ask me about stationery exercise equipment, only real bicycles.


I've been a bicycle mechanic off and on for many years.I taught bicycle mechanics for several years at the Boston Center for Adult Education.I have written a great many articles for bicycle magazines.I have an extensive bicycle-related Website,see: own 30-odd bicycles, some of them very odd indeed!I also worked for several years as a camera repairman.

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