Crank Length

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cyclespeed
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Joined: Mon Jun 06, 2016 8:45 am

by cyclespeed

I really wouldn't worry about the whole CofG thing.

I've progressively raised my saddle by about 20mm over the last few years (only in part due to shorter cranks), and it hasn't done my riding or descending any harm at all. CofG never even crossed my mind. From what I can remember, noone overtook me on any of the 3 descents in the Etape du Tour, and I was at the pointy end!

I've got my eyes open for 165mm cranks. I was curious to canvas opinion on this whole issue, and nothing I've seen so far has changed my mind. Will report back when they're on.*


*obviously those that consider personal experience completely pointless need not set a reminder in their diary......
Last edited by cyclespeed on Tue Sep 06, 2016 12:03 pm, edited 1 time in total.

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wingguy
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by wingguy

Dez33 wrote:
mattr wrote:There are actually some proper tests around on the net. Rather than a GCN video.

They basically say the same thing. Crank length makes little or no difference.


Yes there is. Google J.C. Martin crank length and you will get three or four papers. Basically crank length is not a determinant of maximum power production.

Well, not within the range of commercially available crank sizes, however from a JC Martin paper ...maximum cycling power was significantly affected by crank length :wink:

There also isn't anything in the paper that I could see regarding body position on the bike during testing, or any exploration of the impact on extreme aero positions.

11.4
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Joined: Tue May 23, 2006 4:33 am

by 11.4

That study is very artificial and has a number of flaws. It doesn't bear any resemblance to actual cycling and definitely not to anything resembling racing cycling, whether on the road or on the track. Time to start over again.

This isn't just about morphology and limb lengths. It's also about flexibility, impairment of one's diaphragm, hip impingement issues, whether one has (or is prone to) spurs in the ankles, torso strength, and a host of other matters. Effectively, crank arm length is a personal decision and there's no one formula to describe which crank length to choose. I personally encourage riders I'm working with to check out shorter cranks, but only in the context of a repositioning and to improve overall performance. If that doesn't result in tangible and enduring performance improvement, then short crank arms aren't for them, I deny everything I ever said to them, and tell them that they should try long crank arms.

Seriously, don't follow what someone else has found to work. You might as well use their saddle height without considering whether it fits you.

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cyclespeed
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by cyclespeed

11.4 wrote:That study is very artificial and has a number of flaws. It doesn't bear any resemblance to actual cycling and definitely not to anything resembling racing cycling, whether on the road or on the track. Time to start over again.

This isn't just about morphology and limb lengths. It's also about flexibility, impairment of one's diaphragm, hip impingement issues, whether one has (or is prone to) spurs in the ankles, torso strength, and a host of other matters. Effectively, crank arm length is a personal decision and there's no one formula to describe which crank length to choose. I personally encourage riders I'm working with to check out shorter cranks, but only in the context of a repositioning and to improve overall performance. If that doesn't result in tangible and enduring performance improvement, then short crank arms aren't for them, I deny everything I ever said to them, and tell them that they should try long crank arms.

Seriously, don't follow what someone else has found to work. You might as well use their saddle height without considering whether it fits you.


All good points, and some riders simply won't adapt well to shorter cranks. We are indeed all different.

But if I had a mate on 175's who was interested in experimenting and changing crank length, I would definitely suggest trying 170's before 180's as the disadvantages inherent in the 180's (more leg compression at top stroke, less chance to get aero, etc.) seem to outweigh any potential advantage.

11.4
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by 11.4

cyclespeed wrote:All good points, and some riders simply won't adapt well to shorter cranks. We are indeed all different.

But if I had a mate on 175's who was interested in experimenting and changing crank length, I would definitely suggest trying 170's before 180's as the disadvantages inherent in the 180's (more leg compression at top stroke, less chance to get aero, etc.) seem to outweigh any potential advantage.


Riders don't adapt at times to shorter cranks, sometimes to longer cranks. As I just said, there are simply too many variables at work for one metric alone to define the correct length.

I personally ride 165's and for a number of reasons they work better for me. As I said, I tend to fit riders towards shorter cranks because they offer a few more advantages than longer cranks do. But I don't try to press it if they don't offer better results. As I said.

A very few years ago it was anathema to suggest riding shorter cranks on the road. Even a short rider like Bettini on 170's was ridiculed for riding such short cranks later in his career. I've just been trying to ensure that people understand that short cranks aren't necessarily inferior and while working with a couple national teams have seen a stronger acceptance of short crank arms. Too often those bogus research papers bend the thoughts of coaches, trainers, and riders, when in the end, the one and only real metric for how to do anything on a bike is your ability to win.

Dez33
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Joined: Thu Jun 25, 2015 9:02 am

by Dez33

wingguy wrote:
Dez33 wrote:
mattr wrote:There are actually some proper tests around on the net. Rather than a GCN video.

They basically say the same thing. Crank length makes little or no difference.


Yes there is. Google J.C. Martin crank length and you will get three or four papers. Basically crank length is not a determinant of maximum power production.

Well, not within the range of commercially available crank sizes, however from a JC Martin paper ...maximum cycling power was significantly affected by crank length :wink:


The entire sentence from the 2001 paper is ...

Even though maximum cycling power was significantly affected by crank length, use of the standard 170-mm length cranks should not substantially compromise maximum power in most adults.


The most recent 2011 study is here http://custom4.us/wp-content/uploads/20 ... ycling.pdf

Conclusions: These data demonstrate that crank length does not affect
relative joint-specific power once the effects of pedaling rate and pedal speed are accounted for. Our results thereby substantiate previous
findings that crank length per se is not an important determinant of maximum cycling power production


I will come back later and edit and add a link to another recent Martin document where I'm pretty sure your other points were addressed. If anyone wants to find the link it's in the middle of an old cyclingnews thread where Martin actually posted for a bit explaining a few things about the studies.

It's all interesting reading if you have the time :beerchug:

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cyclespeed
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by cyclespeed

Going back to the extra ground clearance element of shorter cranks, I made a short vid explaining how to quickly calculate your own bike's strike angle using 4 measurements.

https://www.youtube.com/watch?v=kDvXX_xiRGo

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