Crank Lengths- What's the Difference?

[zac _sprint]

I currently have 170mm cranks on my road bike.

If I put on 172.5mm or 175mm cranks what are the advantages and disadvantages of doing so for flat road riding and hill climbing?

 

[531Aussie]

How tall are you and what's your inside leg measurement?

if you're really keen, here's a VERY long thread on this topic, with some interesting anecdotes.

http://www.cyclingforums.com/showthread.php?t=11281

Many people claim, and I'm one of them, that more power is achieved with slightly longer cranks. This is suitable for longer, steady-state work, such as time-trials or hill climbing. I'm a smidge under 6ft, and I recently went from 175s to 180s, and I love them, although I'd like to try 177.5. I'll never go back to 175s -- mind you, I've never been a sprinter's asshole

Indurain (6ft 2", multiple Tour winner) used 180mm cranks, and 190mm cranks for some time-trials, including his "hour record" attempt. Another very tall dude just broke the hour record with 190mm cranks. Jan Ullrich and Lance Armstrong use 177.5mm........BUT, none of these guys are sprinters.

The downside to longer cranks seems to be that sprinters cannot sprint as fast because it's harder to get up, and maintain fast pedal rpms.

Basically, if you're a fast-twitch, sprinter type, you'd wanna be on slightly shorter cranks, and if you're a slow-twitch, "grinder" type, you might wanna consider an increase in crank length.



These guys argue a pretty good case for longer cranks, although I think their formulas result in a crank length that is a bit too long.
http://www.zinncycles.com/cranks.aspx
http://www.cranklength.info/

This guy argues a pretty good case for "normal" length cranks
http://www.bsn.com/Cycling/cranks.html

 

[artmichalek]

Jan Ullrich and Lance Armstrong use 177.5mm........BUT, none of these guys are sprinters.

I'm pretty sure Lance isn't using cranks that long, which is part of the reason why he's been consistently blowing Jan off of his wheel in the mountains the past few years. In addition to sprinting, the short crank/high cadence approach makes it a lot easier to accelerate and counter attacks while climbing.

 

[wilmar13]

I'm pretty sure Lance isn't using cranks that long, which is part of the reason why he's been consistently blowing Jan off of his wheel in the mountains the past few years. In addition to sprinting, the short crank/high cadence approach makes it a lot easier to accelerate and counter attacks while climbing.

*- I would want to add the caveat that it depends on your preferred pedaling style. I am a power rider who likes cadence of about 80-95 but I sprint better with longer cranks, because I can't spin over 100 all that well, and the additional torque I can create at a lower rpm still makes more power than the lower torque with high rpms... for diesel riders (like me) longer cranks are probably better for all situations, even sprinting.