The importance of crank length to the cyclist.

[FrankDay]

And the point is that with a shorter crank and larger gears that "position" becomes more defined, not less. A well-trained rider has a broader and smoother application of power. Does that apply to everyone? No? Does it apply to most good cyclists? Yes. The appropriately added leverage via longer cranks is unique to individual riders, in my experience but nothing either of you proponents have offerred for evidence supporting shorter cranks is convincing.

But, by the same token, what is the evidence that "longer" cranks is superior or that the "appropriately added leverage via longer cranks is unique to individual riders".

The Sheldon Brown article points out the issue very clearly. The only "leverage" that matters is the total leverage between the pedal and the ground. Since power is simply a matter of average force on the pedal and pedal speed it is clear that we should be looking at how crank length affects ones ability to apply that average force to the pedals thousands of time an hour. Since it is obvious crank length affects the ROM and angles the hip and knee joints I think we can assume there would be an effect. Where are the studies that look at the effect? Nowhere that I can see. So, while you may not be convinced by my musing and the reports of others, I don't see why you would think anyone would find your point of view any more convincing in view of the lack of scientific support for it.

And, this is only considering the affect of crank length on power and ignores the potential aerodynamic benefits

 

[CoachFergie]

And, this is only considering the affect of crank length on power and ignores the potential aerodynamic benefits

Aerodynamic benefits the majority can achieve without changing crank length.

 

[onetrack]

Aerodynamic benefits the majority can achieve without changing crank length.

Actually, I'll take John Cobb's stance on aerodynamic positioning over yours. thanks!

 

[CoachFergie]

I will take data over opinion if that is okay with people.

 

[FrankDay]

I will take data over opinion if that is okay with people.

 

[CoachFergie]

That is not data, that is an opinion with some numbers associated to it. Bit like a marketing claim that product X improves power by 40%.

Now if you had the wind tunnel data showing this chaps frontal area had improved by 30% in one aero position from another and power data showing a 25 min improvement in an Ironman you might have a case.

 

[Oldman]

But, by the same token, what is the evidence that "longer" cranks is superior or that the "appropriately added leverage via longer cranks is unique to individual riders".

The Sheldon Brown article points out the issue very clearly. The only "leverage" that matters is the total leverage between the pedal and the ground. Since power is simply a matter of average force on the pedal and pedal speed it is clear that we should be looking at how crank length affects ones ability to apply that average force to the pedals thousands of time an hour. Since it is obvious crank length affects the ROM and angles the hip and knee joints I think we can assume there would be an effect. Where are the studies that look at the effect? Nowhere that I can see. So, while you may not be convinced by my musing and the reports of others, I don't see why you would think anyone would find your point of view any more convincing in view of the lack of scientific support for it.

And, this is only considering the affect of crank length on power and ignores the potential aerodynamic benefits

"pedal and the ground"? Sounds like using 90 degrees of rotation is your total basis for pedal stroke and "aerodynamics" picks up the slack. My view should be more convincing as it is backed by the performances World Champions and the World records of the riders using the techniques.

 

[onetrack]

That is not data, that is an opinion

"...I conducted a wind tunnel test..."-John Cobb

and btw, no one is claiming 30% reduction in frontal area. but the world's foremost authority on aerodynamics in cycling has seen a 30% reduction in "DRAG".

 

[onetrack]

"pedal and the ground"? Sounds like using 90 degrees of rotation is your total basis for pedal stroke and "aerodynamics" picks up the slack. My view should be more convincing as it is backed by the performances World Champions and the World records of the riders using the techniques.

I think you are misunderstanding. "pedal to ground" meaning distance your foot travels vs. distance the rubber on your tire travels across the road. your "view" takes into account no variables. put those same elite riders on shorter cranks with gearing to correct for the gain ratio, and I'm willing to bet they'd be faster.

 

[CoachFergie]

"...I conducted a wind tunnel test..."-John Cobb

and btw, no one is claiming 30% reduction in frontal area. but the world's foremost authority on aerodynamics in cycling has seen a 30% reduction in "DRAG".

Then he will be able to provide the numbers that showed a rider saw a 30% reduction in drag from one aero position to another just from a change in crank length.

Still says nothing about whether they can maintain power in that position or can hold that position for the an Ironman cycle section.

Till then your opinion on his opinion has been duly noted.

 

[Oldman]

I think you are misunderstanding. "pedal to ground" meaning distance your foot travels vs. distance the rubber on your tire travels across the road. your "view" takes into account no variables. put those same elite riders on shorter cranks with gearing to correct for the gain ratio, and I'm willing to bet they'd be faster.

Perhaps you're correct about misunderstanding your "data". As I've pointed out I've been exposed to those elite riders for some time. They train on the track, in wind tunnels and have explored crank lengths. Some I've trained with from early teens to World team and they are willing to try everything so very few variables went unexplored. As for betting...how much do you have? Probably a stake in Frank's company? Sorry, that's a sucker bet.

 

[veganrob]

Then he will be able to provide the numbers that showed a rider saw a 30% reduction in drag from one aero position to another just from a change in crank length.

Still says nothing about whether they can maintain power in that position or can hold that position for the an Ironman cycle section.

Till then your opinion on his opinion has been duly noted.

100% correct.
The ability to hold a position can change dramatically from a wind tunnel test, to 2km race to a 200km race

 

[onetrack]

30 is a number.

Holding an aggressive position is much easier with shorter cranks.

 

[FrankDay]

They train on the track, in wind tunnels and have explored crank lengths.

Perhaps you could give us a little more data as to how those elite riders "explored" crank length and what they found. We have Martin's data when he "explored" this subject between 120 and 220 mm and we have the anecdotal reports here where people have gone as short as 80 mm.

Just exactly what lengths did your riders experiment with? Just how did they do the experiment? What did they find?

 

[CoachFergie]

30 is a number.

Holding an aggressive position is much easier with shorter cranks.

Your opinion has been duly noted.

 

[Boeing]

this is a great thread. I have come to the conclusion that crank arm length is important.

special props to CoahLergie and FrankNight for their well documented debate

 

[Night Rider]

this is a great thread. I have come to the conclusion that crank arm length is important.

The most important thing about crank arms is the engine turning them I will stick to my vanilla 172.5mm's until it's proven anything else is better.

172.5mm by some coincidence is exactly 41% of my tibia length so I guess I was lucky buying the correct length. Maybe these bike manufacturers know a little bit about what length cranks to put on each size bike.

 

[FrankDay]

The most important thing about crank arms is the engine turning them I will stick to my vanilla 172.5mm's until it's proven anything else is better.

172.5mm by some coincidence is exactly 41% of my tibia length so I guess I was lucky buying the correct length. Maybe these bike manufacturers know a little bit about what length cranks to put on each size bike.

Would anyone please let me know the basis for any of these crank length formulas?

 

[CoachFergie]

Would anyone please let me know the basis for any of these crank length formulas?

Same as meaningless equation like a gain ratio.

 

[onetrack]

Same as meaningless equation like a gain ratio.

yeah, because the relationship between how far the pedal travels and how far the tire travels is meaningless.

 

[CoachFergie]

Glad to see we can agree. It is meaningless.

 

[srs428]

how do i access the web site with the research data?

 

[CoachFergie]

This is the summary of the work done by James Martin.

http://www.plan2peak.com/files/32_article_JMartinCrankLengthPedalingTechnique.pdf

 

[Oldman]

this is a great thread. I have come to the conclusion that crank arm length is important.

special props to CoahLergie and FrankNight for their well documented debate

I agree, it is important. And with that we should move on...

 

[Night Rider]

Would anyone please let me know the basis for any of these crank length formulas?

The place I found the 41% measurement was the Jim Martin 2001 study, which also used a 20% of leg length measurement. Both came out the same for me, 172.5mm. Don't know the basis of their calculation though. I only did the exercise for interests sake to see how it compared to what I was already using.

FWIW when I did the fit calculation from the Competitive Cyclists website a few years back it also came out with around the same length crank, they probably use the same formula.