Where did the idea of proportional crank length come from?
It might be completely n=1 but being of longer legs I actually feel better and more stable on a shorter crank, as I feel a bit more locked in.
Just my own findings.
Where did the idea of proportional crank length come from? .
I believe it originated here on Slowtwitch by a fellow named Dave Campbell who promoted it for many years.
Hugh
Hahaha
Maybe this is why he’s finding short cranks better?
Bets not to mention him, he’s like the candyman, he’ll turn up to ruin this thread in a minute.
Oh Snap!!!
Where did the idea of proportional crank length come from? .
I believe it originated here on Slowtwitch by a fellow named Dave Campbell who promoted it for many years.
Hugh
Thats for making me feel so special.
Where did the idea of proportional crank length come from? .
I believe it originated here on Slowtwitch by a fellow named Dave Campbell who promoted it for many years.
Hugh
Thats for making me feel so special.
Well Dave, I believe most would agree that you are pretty special;)
Where did the idea of proportional crank length come from? .
I believe it originated here on Slowtwitch by a fellow named Dave Campbell who promoted it for many years.
Hugh
Thats for making me feel so special.
Well Dave, I believe most would agree that you are pretty special;)
Say that to my face next time
Where did the idea of proportional crank length come from?
It might be completely n=1 but being of longer legs I actually feel better and more stable on a shorter crank, as I feel a bit more locked in.
Just my own findings.
Notwithstanding any previous posts by folks here, I think the idea is pretty old, I think it far precedes even the existence of this venerable forum. My guess is that the idea came from the fact that nearly all other things on bikes are (or should be) generally proportional to rider size. And that proportional things on bikes historically seemed to work better than things that weren’t proportional.
For example, things like frame size, seat height, top tube length, stem length, handlebar width, cycling shoe size, even wheel diameter, etc., all of these things typically have (or should have) a proportional relationship to rider size. So it does stand to reason that, **for a given optimal set up **(i.e., an optimal road set up, or an optimal TT bike set up, or an optimal XC MTB set up), it might be better for a 4’6’’ tall rider to possibly use different length cranks than a 6’6’’ tall rider, and vice-versa.
Where did the idea of proportional crank length come from?
It might be completely n=1 but being of longer legs I actually feel better and more stable on a shorter crank, as I feel a bit more locked in.
Just my own findings.
Notwithstanding any previous posts by folks here, I think the idea is pretty old, I think it far precedes even the existence of this venerable forum. My guess is that the idea came from the fact that nearly all other things on bikes are (or should be) generally proportional to rider size. And that proportional things on bikes historically seemed to work better than things that weren’t proportional.
For example, things like frame size, seat height, top tube length, stem length, handlebar width, cycling shoe size, even wheel diameter, etc., all of these things typically have (or should have) a proportional relationship to rider size. So it does stand to reason that, **for a given optimal set up **(i.e., an optimal road set up, or an optimal TT bike set up, or an optimal XC MTB set up), it might be better for a 4’6’’ tall rider to possibly use different length cranks than a 6’6’’ tall rider.
Yep, pretty simple idea
Where did the idea of proportional crank length come from? .
I believe it originated here on Slowtwitch by a fellow named Dave Campbell who promoted it for many years.
Hugh
Thats for making me feel so special.
Well Dave, I believe most would agree that you are pretty special;)
Say that to my face next time
c’mon, lighten up.
besides, you’re 8 feet tall and weigh 50 lbs… what are you going to do if someone does say anything to your face?
Where did the idea of proportional crank length come from?
It might be completely n=1 but being of longer legs I actually feel better and more stable on a shorter crank, as I feel a bit more locked in.
Just my own findings.
Notwithstanding any previous posts by folks here, I think the idea is pretty old, I think it far precedes even the existence of this venerable forum. My guess is that the idea came from the fact that nearly all other things on bikes are (or should be) generally proportional to rider size. And that proportional things on bikes historically seemed to work better than things that weren’t proportional.
For example, things like frame size, seat height, top tube length, stem length, handlebar width, cycling shoe size, even wheel diameter, etc., all of these things typically have (or should have) a proportional relationship to rider size. So it does stand to reason that, **for a given optimal set up **(i.e., an optimal road set up, or an optimal TT bike set up, or an optimal XC MTB set up), it might be better for a 4’6’’ tall rider to possibly use different length cranks than a 6’6’’ tall rider, and vice-versa.
Confounding factor though is that racing isn’t done in height categories, so ultimately rpms need to go through the gearing to be translated into a speed which is NOT proportional to body size. so a 4’6 rider might prefer cranks that are a bit shorter than the 6’6 rider, it doesn’t really follow that the change should be proportional. Proportional changes in crank length would have the 4’6 rider on 150mm cranks and the 6’6 rider on 216mm cranks…
Kirby Palm from the early days of the internet: http://www.nettally.com/palmk/crankset.html
He makes seemingly sound arguments, none of which are supported by research.
Cheers,
Jim
Not sure I follow your post, but …
Confounding factor though is that racing isn’t done in height categories
If that is the case, then none of the other size related stuff should be proportionally sized either ?
So a 4’6 rider might prefer cranks that are a bit shorter than the 6’6 rider.
Again, not sure I follow, but why not the 4’6’’ rider preferring longer cranks than the 6’6’’ rider?
Where did the idea of proportional crank length come from? .
I believe it originated here on Slowtwitch by a fellow named Dave Campbell who promoted it for many years.
Hugh
Thats for making me feel so special.
Well Dave, I believe most would agree that you are pretty special;)
Say that to my face next time
c’mon, lighten up.
besides, you’re 8 feet tall and weigh 50 lbs… what are you going to do if someone does say anything to your face?
My point was that for someone to spend their time attacking someone on line, then have the guts to introduce themselves to me at a world championship event like he was this real nice guy, just calling him out. If he tried to talk to me in the future, I would just smile and walk away.
Not sure I follow your post, but …
Confounding factor though is that racing isn’t done in height categories
If that is the case, then none of the other size related stuff should be proportionally sized either ?
So a 4’6 rider might prefer cranks that are a bit shorter than the 6’6 rider.
Again, not sure I follow, but why not the 4’6’’ rider preferring longer cranks than the 6’6’’ rider?
they might. hence the word, might.
the other size related stuff is not directly related to applying power. only indirectly. you still need to get to rpm x gear incheso = velocity (inches per minute). handlebar width has nothing to do with that. nor does frame size. nor does wheel size, since it’s just a component of the gear inch number.
ETA - thought experiment - if everything else remains constant, including gear ratio, velocity, resistance, and power, then what happens to pedal force as the crankarm shortens? What happens to rpms and gear ratio if you want to maintain the same velocity?
Where did the idea of proportional crank length come from? .
I believe it originated here on Slowtwitch by a fellow named Dave Campbell who promoted it for many years.
Hugh
Thats for making me feel so special.
Well Dave, I believe most would agree that you are pretty special;)
Say that to my face next time
Did you actually mean ‘Thanks’ or ‘Thats’
…and is that a threat, challenge or request?
lol popcorn time. . .
Jim, I think well prior to the netally stuff, companies still made different sized cranks and other proportionally sized bike parts and components. Why do you think that common sense seems to run counter to the research regarding crank length? What do you think is flawed, the common sense? The research? A little of both?
Another related question, is any part of bike fit (anything at all–for example any of the typical anecdotally-accepted tri bike fit guidelines and accepted wisdom from various tri bike schools of thought) actually supported by decent peer-reviewed reseach?
My understanding (but correct me if I am wrong) is that nearly none of it is. Isn’t all of bike fit just common sense totally unsupported by research? Serious question.
thanks,
Greg
Why do you think that common sense seems to run counter to the research regarding crank length? What do you think is flawed, the common sense? The research? A little of both?
The research (much of which comes from my lab) is solid. The common sense is also solid but incomplete. Muscles have force-velocity characteristics as well as activation and deactivation dynamics. That is, muscles must become activated, produce force while shortening, relax, and undergo lengthening each cycle. Once all those factors interact, crank length simply doesn’t matter for maximal power or for submaximal efficiency. At least not within a really large range.
Another related question, is any part of bike fit (anything at all–for example any of the typical anecdotally-accepted tri bike fit guidelines and accepted wisdom from various tri bike schools of thought) actually supported by decent peer-reviewed reseach?
I don’t follow any of the fitting protocols so I simply can’t comment. Here’s my simplistic approach to fitting for aerodynamics and crank length together.
- Decide how close to horizontal you want your torso. Closer to horizontal is generally more aero but requires really holding your head up to look ahead. You could do this part of the fit with cranks stationary and horizontal, its just to find out how low you’re really willing to go.
- Once you have dialed in the seat-relative-to-elbow pad position for how low you want to go, you can determine crank length. Proper crank length would be the one that gives you a reasonable hip angle as you come over the top. This is also influenced by fore-aft saddle position which serves to rotate your body about the bottom bracket. Of course you must adjust seat and elbow pad height to accommodate each crank length. If you’re tall and thin, regular sized cranks will probably work just fine. If you’re under about 5’10" or thickly built, you’ll likely need shorter cranks (unless you want to sit up pretty high).
- Done.
I went through this process to set up a UCI legal position (nose of saddle 5cm behind bb) for myself for track cycling. I wanted absolutely horizontal torso. At 5’8" 160lb, I needed 145mm cranks to make that rideable. For triathlon I wouldn’t need to go that short because the rules allow a much more forward saddle position. Probably a good place to start any fitting procedure is with the saddle as far forward as the rules allow.
Cheers,
Jim
PS I am not a bike fitter except for myself. I have, however, published several papers on cycling crank length and cycling aerodynamics, and spent untold hours in wind tunnels.
Beautifully stated. When you understand Jim’s research, crank length takes its rightful place as a bike fit metric, not as a power enhancing gimmick.