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Crank Length
I have always considered crank length to be something meaningless depending, of course, on not being extreme. For example, I have ridden with 170mm cranks on road bikes for years and years and as long as 174mm on mountain bikes, and never noticed any difference between the lengths. Added to this the charts that I have found tell me that, with my height, I should be riding something like 165mm cranks. However :-) I have two bikes, in Bangkok, both essentially the same. Same frame measurements, same seat height, same distance from the saddle to the handle bars, same gearing and weights within about a kilogram. the older bike - frame and forks - weighs 3.2 Kg. the newer 2.5 Kg. While I don't make a fetish about it I did notice that the last time I rode the older bike on my usual Wednesday loop I seemed a bit faster for the same apparent effort. I checked the sprockets and I was riding one cog higher gear ratio on the older heavier bike. I would usually ride in a 58" gear and that day I was using a 61" gear. When I got home I did some checking and found that the New BKK Bike has 170mm cranks and the Old BKK Bike has 172.5mm cranks. Given that the usual recommendation for a guy my height is a 165mm crank but in practice I am finding a 172.5mm crank seems faster than the shorter crank, for the same effort, is the formula wrong? My usual pedal RPM for any crank is 80 - 100 rpm. Any comments or enlightenment? -- cheers, John B. |
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#2
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Crank Length
On Thursday, October 20, 2016 at 7:42:53 PM UTC-7, John B. wrote:
I have always considered crank length to be something meaningless depending, of course, on not being extreme. For example, I have ridden with 170mm cranks on road bikes for years and years and as long as 174mm on mountain bikes, and never noticed any difference between the lengths. Added to this the charts that I have found tell me that, with my height, I should be riding something like 165mm cranks. However :-) I have two bikes, in Bangkok, both essentially the same. Same frame measurements, same seat height, same distance from the saddle to the handle bars, same gearing and weights within about a kilogram. the older bike - frame and forks - weighs 3.2 Kg. the newer 2.5 Kg. While I don't make a fetish about it I did notice that the last time I rode the older bike on my usual Wednesday loop I seemed a bit faster for the same apparent effort. I checked the sprockets and I was riding one cog higher gear ratio on the older heavier bike. I would usually ride in a 58" gear and that day I was using a 61" gear. When I got home I did some checking and found that the New BKK Bike has 170mm cranks and the Old BKK Bike has 172.5mm cranks. Given that the usual recommendation for a guy my height is a 165mm crank but in practice I am finding a 172.5mm crank seems faster than the shorter crank, for the same effort, is the formula wrong? My usual pedal RPM for any crank is 80 - 100 rpm. Any comments or enlightenment? How old are you? |
#3
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Crank Length
On Thu, 20 Oct 2016 23:05:30 -0700 (PDT), Doug Landau
wrote: On Thursday, October 20, 2016 at 7:42:53 PM UTC-7, John B. wrote: I have always considered crank length to be something meaningless depending, of course, on not being extreme. For example, I have ridden with 170mm cranks on road bikes for years and years and as long as 174mm on mountain bikes, and never noticed any difference between the lengths. Added to this the charts that I have found tell me that, with my height, I should be riding something like 165mm cranks. However :-) I have two bikes, in Bangkok, both essentially the same. Same frame measurements, same seat height, same distance from the saddle to the handle bars, same gearing and weights within about a kilogram. the older bike - frame and forks - weighs 3.2 Kg. the newer 2.5 Kg. While I don't make a fetish about it I did notice that the last time I rode the older bike on my usual Wednesday loop I seemed a bit faster for the same apparent effort. I checked the sprockets and I was riding one cog higher gear ratio on the older heavier bike. I would usually ride in a 58" gear and that day I was using a 61" gear. When I got home I did some checking and found that the New BKK Bike has 170mm cranks and the Old BKK Bike has 172.5mm cranks. Given that the usual recommendation for a guy my height is a 165mm crank but in practice I am finding a 172.5mm crank seems faster than the shorter crank, for the same effort, is the formula wrong? My usual pedal RPM for any crank is 80 - 100 rpm. Any comments or enlightenment? How old are you? 84. -- cheers, John B. |
#4
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Crank Length
Same make and model of tires and same tire pressure on both bikes? 58 to 61 gear inches is about a 5% difference which could be easily accounted for by something other than the difference in crank length. Tires and tire pressure are the first thing that came to mind but for a single ride, there could be other variables at work.
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Crank Length
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#7
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Crank Length
On Thursday, October 20, 2016 at 7:42:53 PM UTC-7, John B. wrote:
I have always considered crank length to be something meaningless depending, of course, on not being extreme. For example, I have ridden with 170mm cranks on road bikes for years and years and as long as 174mm on mountain bikes, and never noticed any difference between the lengths. Added to this the charts that I have found tell me that, with my height, I should be riding something like 165mm cranks. However :-) I have two bikes, in Bangkok, both essentially the same. Same frame measurements, same seat height, same distance from the saddle to the handle bars, same gearing and weights within about a kilogram. the older bike - frame and forks - weighs 3.2 Kg. the newer 2.5 Kg. While I don't make a fetish about it I did notice that the last time I rode the older bike on my usual Wednesday loop I seemed a bit faster for the same apparent effort. I checked the sprockets and I was riding one cog higher gear ratio on the older heavier bike. I would usually ride in a 58" gear and that day I was using a 61" gear. When I got home I did some checking and found that the New BKK Bike has 170mm cranks and the Old BKK Bike has 172.5mm cranks. Given that the usual recommendation for a guy my height is a 165mm crank but in practice I am finding a 172.5mm crank seems faster than the shorter crank, for the same effort, is the formula wrong? My usual pedal RPM for any crank is 80 - 100 rpm. Any comments or enlightenment? -- cheers, John B. What is the frame materials? After dumping my carbon and aluminum bikes and going back to steel I am much faster everywhere but steep climbs. Steel rides SO much more comfortably that I think a lot less of dodging pot holes and more about riding. |
#8
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Crank Length
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