Crank length 170mm, 172.5mm, 175mm
11-17-10, 05:14 PM
#26
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|3iker, One thing I forgot to mention is that seat post height is adjusted differently for the two different crankarm lengths I have on my two most used bicycles... The bikes are essentially identical otherwise and seat post height was the same when both had 172.5 mm crankarms. Technically I don't know if it makes a difference and hopefully some gurus will respond. My intent was to keep my body the same WRT the BB spindle or at least to the bottom of the pedal stroke so I lowered the saddle 2.5 mm. Perhaps this is why I don't feel any difference between the two for more than a minute or so.(?)
Brad
PS I lowered the saddle to prevent hip rocking.
Brad
PS I lowered the saddle to prevent hip rocking.
Last edited by bradtx; 11-17-10 at 05:20 PM. Reason: ps
11-17-10, 06:17 PM
#27
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So if I get a 170mm I should raise the saddle height by 2.5mm? And lower 2.5mm if it's 175mm.
11-17-10, 07:25 PM
#28
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Yes, generally seat height is determined off the bottom of the pedal stroke, so shorter arms would call for raising the saddle to compensate.
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11-17-10, 07:34 PM
#29
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you have to slide the saddle back slightly too, otherwise you'll be putting more weight on your arms. Unless that's what you're aiming for.
I find that for a 5mm shorter crank, you want to slide the saddle back by 10mm and raise it by 4mm or raise the saddle by 5mm and move your cleats back by 5mm. 2x lateral, 0.866x vertical change in saddle position for every 1mm of difference in the crank.
but it depends on what you're aiming for. For touring, or commuting, basically anything leisurely where peak power doesn't matter, sliding the cleats back is better.
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Last edited by AEO; 11-17-10 at 07:37 PM.
11-18-10, 07:53 AM
#30
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Another thing, and it's thinking aloud, my knee doesn't have a flexability issue so the longer crank arm and lowered saddle height (which raises the knee in relation to the hips) had no effect when my injured knee's pedal was at 12 o'clock. With ITBS you maybe more sensitive to the more acute hip/knee angle, even if just lowering the saddle with the same crankset.
Brad
