following on from the questions about very small frames viewtopic.php?f=1&t=341956 this is about cranks
now I know there has been some debate on many forums about whether people (average height people typically) can tell the difference between 170 and 175mm cranks. This is more about at the extremes, where just seeing someone of petite stature on an adult bike there can be an issue.
This is all based on the saddle position being based on the pedal position at the bottom of the pedal stroke. A longer crank will mean the saddle is lower, by 1cm if comparing 175 with 165mm cranks. At the the same time the pedal at the top of the stroke will therefore be 2cm closer to the saddle when comparing 175 with 165mm cranks. With longer legs this may not make much difference but is a much bigger impact with smaller legs. This is very different to crank lengths with track bikes etc when a lot is about ground clearance and avoiding pedal strike, bike upright on a banked track etc. There is also the thing on toe overlap when cranks are horizontal on smaller frames. This is also part of the reason for smaller wheels on smaller road frames, 650c instead of 700c. I'm not worried about gearing or the leverage effect, that can all be sorted with changing gear ratios.
So after all that I was wondering whether others had looked at this. Even on the specific women's smaller bikes (the wife's current 14" frame WSD trek for example) the cranks seem to be 170mm which seems as much about mass availability. The reality seems that even if someone wanted 160-165mm cranks (excluding BMX and track) that there are very few alternatives, some of the shimano XT over the years had a 165mm alternative not that have ever seen any and then the old touring sets like TA from the 1970s.
has anybody shorter tried the shorter crank route ?
now I know there has been some debate on many forums about whether people (average height people typically) can tell the difference between 170 and 175mm cranks. This is more about at the extremes, where just seeing someone of petite stature on an adult bike there can be an issue.
This is all based on the saddle position being based on the pedal position at the bottom of the pedal stroke. A longer crank will mean the saddle is lower, by 1cm if comparing 175 with 165mm cranks. At the the same time the pedal at the top of the stroke will therefore be 2cm closer to the saddle when comparing 175 with 165mm cranks. With longer legs this may not make much difference but is a much bigger impact with smaller legs. This is very different to crank lengths with track bikes etc when a lot is about ground clearance and avoiding pedal strike, bike upright on a banked track etc. There is also the thing on toe overlap when cranks are horizontal on smaller frames. This is also part of the reason for smaller wheels on smaller road frames, 650c instead of 700c. I'm not worried about gearing or the leverage effect, that can all be sorted with changing gear ratios.
So after all that I was wondering whether others had looked at this. Even on the specific women's smaller bikes (the wife's current 14" frame WSD trek for example) the cranks seem to be 170mm which seems as much about mass availability. The reality seems that even if someone wanted 160-165mm cranks (excluding BMX and track) that there are very few alternatives, some of the shimano XT over the years had a 165mm alternative not that have ever seen any and then the old touring sets like TA from the 1970s.
has anybody shorter tried the shorter crank route ?
..... :mrgreen: 
although I'd need to check what taps I've got
