Proper Crank Length

[r_mutt]

i know this has been beaten to death, and endlessly argued over what is "right", so i won't ask you for your arguments, but instead, ask you to post some intelligent links to he topic.

thanks-

:cool:

[dekindy]

I remember reading a study that crankarm length had negligible impact on power output, even if extremely short or long cranks were used. It would impact gear ratio, seat height, cadence, etc. But comparing apples to apples it did not impact power output. If I can find the link to the study I will gladly refer you to it.

[Waldo]

Lennard Zinn's take on it is inseam x .216, which can yield surprising results.
http://www.zinncycles.com/cranks.php

[Lurch]

I remember reading a study that crankarm length had negligible impact on power output, even if extremely short or long cranks were used. It would impact gear ratio, seat height, cadence, etc. But comparing apples to apples it did not impact power output. If I can find the link to the study I will gladly refer you to it.

Are you refering to Sheldon Brown's thoughts on the subject?

Sheldon's Crank Length Article (http://www.sheldonbrown.com/cranks.html)

[r_mutt]

Lennard Zinn's take on it is inseam x .216, which can yield surprising results.
http://www.zinncycles.com/cranks.php


the zinn formula is telling me that i need a 164mm crank!!! i'm short (5-7), but that's a track crank!

since he's only tested his theories on tall riders, maybe it's skewed...

[Peter B]

yeah, and by the same method, and at 5'-8", i need 181mm cranks.

the zinn formula is telling me that i need a 164mm crank!!! i'm short (5-7), but that's a track crank!

since he's only tested his theories on tall riders, maybe it's skewed...

[pbjbike]

Maybe if you posted your inseam and femur length, you'd get some comparable crank lengths that might work for you. It's very subjective.

[r_mutt]

Maybe if you posted your inseam and femur length, you'd get some comparable crank lengths that might work for you. It's very subjective.


my inseam is 76.5cm and my femur length is 58 cm. i'm curious to see if a slightly longer crank will make any kind of difference. currently, i ride a 170.

[93LegendTG]

Kirby Palm's Site:
http://www.nettally.com/palmk/Crankset.html

[Louis]

A poll I took here back in '05 ( Link (http://forums.thepaceline.net/showthread.php?t=7616) ) and a summary of the results:

http://forums.thepaceline.net/attachment.php?attachmentid=4132&stc=1

[r_mutt]

yeah, and by the same method, and at 5'-8", i need 181mm cranks.


at 5-8 you have an 84cm inseam?

[Marcusaurelius]

at 5-8 you have an 84cm inseam?


And for the non metric (like myself) that's a 33 inch inseam for 5' 8" height.
I'm not sure that's possible even with very long legs.

[pbjbike]

You could definitely ride a 172.5 crank, IMO. I have an almost identical inseam and prefer 172's. 175 proved too long on a road bike for me. Check your femur length--58cm seems off. If that's right, you've got a helluva lever there.

[Peter B]

at 5-8 you have an 84cm inseam?

Yep. 33" cycling inseam. 172.5 thank you.

[false_Aest]

Yep. 33" cycling inseam. 172.5 thank you.

Yeah I'm jealous.

[r_mutt]

You could definitely ride a 172.5 crank, IMO. I have an almost identical inseam and prefer 172's. 175 proved too long on a road bike for me. Check your femur length--58cm seems off. If that's right, you've got a helluva lever there.


hmmm don't know why 58cm is written in my notes, i don't know how to properly measure, but it looks like it's 48cm according to my ham-fisted ways.

[ols]

If you have a Computrainer, they sell this to measure the effect of crank arm length on cycling performance (fwiw, I havent got either a CT or this):

http://www.racermateinc.com/varicrank.asp

[Waldo]

yeah, and by the same method, and at 5'-8", i need 181mm cranks.

Give 'em a shot, you neve know. I can lend you a set of 180s. I'm 6'1" and I've been riding 190s for ~4 years. Per Zinn, I should use 192s, but I decided to be conservative and went with cranks 2mm shorter.

[hookookadoo]

Yep. 33" cycling inseam. 172.5 thank you.

I am 5' 7.5" and have relatively long legs and only have a 31.5" inseam. You have two more inches on me. What kind of bike/geometry are you riding? Custom?

[Peter B]

I am 5' 7.5" and have relatively long legs and only have a 31.5" inseam. You have two more inches on me. What kind of bike/geometry are you riding? Custom?


Out of 8 road bikes, 6 are custom. I ride lots of doubles and longer events, and so prefer saddle to bar drop in the 55-60mm range. That puts me in a good aero position given my relatively short torso. Most stock 53s and 54s do not have enough head tube to get me there without excessive spacers once I get my saddle in the right spot. Two stock bikes which do are a 53 Legend (w/ 15mm HT extension) and a Medium Look 595.