CRANK ARM LENGTH

[SwissVan]

http://sheldonbrown.com/gain.html

 

Pretty much where you guys got to in the last discussion - crank length effectively changes gearing (although it is marginal when talking 5mm).

 

Who is this Linnega fellow?

[Capricorn]

i've read somewhere, and apologies that i've yet found the link to that article, is that the real benefit to changing crank length is biomechanical efficiency. You can produce less or more effective power depending on the crank length,but it has nothing to do with pure mechanical leverage as alluded to in another posting.

 

Its a very similar argument to how aero should triathletes go when assuming the aero position:there's a balance point either side of which you are too aero, but you are compressing your diaphragm too much and loosing biomechanical efficiency, and the other side where you gain biomechanical efficiency via improved breathing and reoxygenation, but lose out aerodynamically. Or something to that effect.

 

With the crank length situation,it has to do with your pedalling efficiency linked to hip movement, especially during seated climbs, femur length etc.

[popcorn_skollie]

But, what cadence to you climb at. If its higher (90, 100, +), the shorter crank will enable you to do this, as your legs are moving slower.

 

If you ride a lower cadence (below 80), the longer cranks should enable you to keep a lower force needed to maintain speed, basically grinding a gear easier.

 

Clueless. Wouldn't be able to tell you my cadence in numbers but it certainly varies. Initially what struck me was how much more effort the shorter arms required just by feeling it in the climbs. By extension I assumed that it meant I would now climb slower than before.

 

But for me, ergonomically they are a better fit. And the effort and time taken in switching between gears to feel comfortable in my stride are certainly not missed.

[Captain Fastbastard Mayhem]

i've read somewhere, and apologies that i've yet found the link to that article, is that the real benefit to changing crank length is biomechanical efficiency. You can produce less or more effective power depending on the crank length,but it has nothing to do with pure mechanical leverage as alluded to in another posting.

 

Its a very similar argument to how aero should triathletes go when assuming the aero position:there's a balance point either side of which you are too aero, but you are compressing your diaphragm too much and loosing biomechanical efficiency, and the other side where you gain biomechanical efficiency via improved breathing and reoxygenation, but lose out aerodynamically. Or something to that effect.

 

With the crank length situation,it has to do with your pedalling efficiency linked to hip movement, especially during seated climbs, femur length etc.

Makes sense. Would also be worth a read!

[carbon29er]

I thought European Journal of Applied Physiology is scientific proof?

"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."

 

There is nothing in their paper to suggest "most adults" will produce less or more power using AVAILABLE crank lengths which typically range from 165mm to 180mm. Or was there additional info not included in your link that I missed?

[Capricorn]

well, i tried to find the article, but it was a very long time ago, and only just one article. Hardly a comprehensive round up of the subject.

 

nonetheless, searching now for crank length + biomechanical efficiency yielded many articles on the matter,and it would seem most bunk the argument of a biomechanical loss, except in isolated cases involving rehabilitation. This article has a bunch of slides, but all of them are summarised nicely toward the end of each section the 'study' deals with.

 

The latter sections seem to focus on what the study believes is the most important aspects of cycling: pedal technique, cycling strategy, training, recovery

[jcza]

"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."

 

There is nothing in their paper to suggest "most adults" will produce less or more power using AVAILABLE crank lengths which typically range from 165mm to 180mm. Or was there additional info not included in your link that I missed?

 

 

Believe it or not, the test results showed no statistical difference in maximum power among the three middle crank lengths (145, 170 and 195mm). - See more at: http://www.cervelo.com/en/engineering/ask-the-engineers/crank-length.html#sthash.CrPZA3U4.dpuf

[Wil6]

Mmmmm Captain ...... When I was doing some juggling with cranks for my SS MTB I was told that despite a 32*20 having the same 'ratio' as a 34*22 the 32 would feel easier to pedal due to some leverage effect - could you perhaps comment if they were talking poofie or not?

I dont know why, but I recently changed from 18×32 to 20×34 and I'm much more comfortable with this and find it easier to rotate the crank.

[carbon29er]

Believe it or not, the test results showed no statistical difference in maximum power among the three middle crank lengths (145, 170 and 195mm). - See more at: http://www.cervelo.com/en/engineering/ask-the-engineers/crank-length.html#sthash.CrPZA3U4.dpuf

Isn't that what I wrote? No scientific evidence that crank length affects power?

[jcza]

Isn't that what I wrote? No scientific evidence that crank length affects power?

 

"I thought European Journal of Applied Physiology is scientific proof?"

 

Going around in circles here.... Enjoy Braai day tomorrow

[JA-Q001]

I dont know why, but I recently changed from 18×32 to 20×34 and I'm much more comfortable with this and find it easier to rotate the crank.

 

But you also actually changed your gear ratio from 1.78 to 1.7, so that could be the difference you are feeling.

[Wil6]

But you also actually changed your gear ratio from 1.78 to 1.7, so that could be the difference you are feeling.

Yeah I know, but the difference is more than 0.08 of a difference

[Plentipotential]

Luckily for me I just enjoy riding the bike otherwise I would have to read through some heavy stuff without even knowing if the scientist had ever ridden a bike.

 

What I do know is that when I was forced to change the crank length because I ordered the wrong length an ongoing problem of a saddle sore vanished. What a stroke of luck and bugger all science involved.

[Capricorn]

Luckily for me I just enjoy riding the bike otherwise I would have to read through some heavy stuff without even knowing if the scientist had ever ridden a bike.

 

What I do know is that when I was forced to change the crank length because I ordered the wrong length an ongoing problem of a saddle sore vanished. What a stroke of luck and bugger all science involved.

 

did u size up or down? wild guess would be size down..

[JohnnyReggae]

I don't think that you will even notice a difference between 175 and 170.

 

On my Uni I went from 175 cranks to 150 and the difference was very noticeable and huge. The additional effort/power required especially going uphill was quite big, but at the end of the day I much prefer 150 over 175. I have dual hole cranks so I can go down to 125 if I wanted to, but the control required going downhill is huge and I don't want my knees to take that strain.

[Plentipotential]

did u size up or down? wild guess would be size down..

 

Yes, down to 170 from 175.