The importance of crank length to the cyclist.

[simo1733]

I can see the aero advantage of shorter cranks but a lot of the world tour pro's seem to go for longer cranks on TT bikes.
Does any one know of any of the top TT riders using anything less than 170s ?

 

[FrankDay]

I can see the aero advantage of shorter cranks but a lot of the world tour pro's seem to go for longer cranks on TT bikes.
Does any one know of any of the top TT riders using anything less than 170s ?

My guess is few if any. Several years ago I know Levi Leipheimer was given the recommendation by Max Testa to try in the 145-150 range but the best he was able to bring himself to do was to shorten his cranks to 170. (edit: I know this because Levi called me and asked my what I thought. At the time I was like everyone else and could only think about power so I told him I could make an argument but I didn't think it made a big difference.) It is especially hard to get people who have had great success doing one thing to change. But, even Lance is thinking about this. "My whole career I rode one-seventy-five cranks for both road and time trial," he said. "But, I fell victim to Slowtwitch Forum advice and went to one-seventies. There is even talk of going shorter, but, for me, one-seventy is short enough."

We have been talking to both pros and some of the coaches of some of these pros and it turns out that, apparently, there are no cranks shorter than 170 available from the team sponsors in all of Italy. When we try to talk them into trying it we get the same stuff we have seen here, they simply can't believe it is possible to generate any power on shorter cranks even though they have never experimented with it. Since it is easy to measure power and quite difficult to measure drag focusing on power is much easier than focusing on the totality. Probably why there are entire forums devoted to power and not much thought given to this problem. At least we have gotten a few of the pro triathletes to think about this and put their toes in the water. As we have seen before, this advance in cycling will probably come via triathlon.

I think my advice right now is more for those who are willing to experiment and see what is best for them rather than those who prefer to follow the lead of the pros. I look forward to someone coming here and actually presenting some real data that makes the argument that "longer is better" beyond "that is what the pros ride".

 

[Semper Fidelis]

My guess is few if any. Several years ago I know Levi Leipheimer was given the recommendation by Max Testa to try in the 145-150 range but the best he was able to bring himself to do was to shorten his cranks to 170. (edit: I know this because Levi called me and asked my what I thought. At the time I was like everyone else and could only think about power so I told him I could make an argument but I didn't think it made a big difference.) It is especially hard to get people who have had great success doing one thing to change. But, even Lance is thinking about this. "My whole career I rode one-seventy-five cranks for both road and time trial," he said. "But, I fell victim to Slowtwitch Forum advice and went to one-seventies. There is even talk of going shorter, but, for me, one-seventy is short enough."

We have been talking to both pros and some of the coaches of some of these pros and it turns out that, apparently, there are no cranks shorter than 170 available from the team sponsors in all of Italy. When we try to talk them into trying it we get the same stuff we have seen here, they simply can't believe it is possible to generate any power on shorter cranks even though they have never experimented with it. Since it is easy to measure power and quite difficult to measure drag focusing on power is much easier than focusing on the totality. Probably why there are entire forums devoted to power and not much thought given to this problem. At least we have gotten a few of the pro triathletes to think about this and put their toes in the water. As we have seen before, this advance in cycling will probably come via triathlon.

I think my advice right now is more for those who are willing to experiment and see what is best for them rather than those who prefer to follow the lead of the pros. I look forward to someone coming here and actually presenting some real data that makes the argument that "longer is better" beyond "that is what the pros ride".

levi is a midget of course he would be open to give you and the 140's a call!

U r driveing up a long hill with some short CRANKS.

 

[FrankDay]

levi is a midget of course he would be open to give you and the 140's a call!

That is the point, he wasn't willing to make but tiny changes. Lance is doing the same it seems. Elites are the most difficult to get to change because they have been successful and they attribute their success to what they have done. Plus, they have the most to lose if the change doesn't work out. Change usually comes from lower ranks or from the outside. In recent times for cycling change has generally started in triathlon.

U r driveing up a long hill with some short CRANKS.

Climbing is about power, not crank length. Crank length is accounted for when climbing through gearing. If you can generate a sustainable 350 watts on both 110 mm cranks and 175 mm cranks you should climb exactly the same as long as you are geared properly to be at the cadence necessary to allow you to generate the power. (You might even climb a little faster on the shorter cranks since they should weigh less.) If you aren't geared properly you aren't going to climb well regardless of how long your cranks are.

 

[coapman]

What is the effect of a shorter crank as you bring the PC type crank from 5 to 8 o'c and 10 to 1 o'c.

 

[FrankDay]

What is the effect of a shorter crank as you bring the PC type crank from 5 to 8 o'c and 10 to 1 o'c.

I am not sure what you are asking exactly. The only difference between PC's and regular cranks is that the circular movement of the foot has to be done actively, there can be nothing passive (one leg helping the other) because any lack of active "driving" during any part of the stroke means the crank stops moving. So, going to shorter cranks simply means the range of motion for this part of the stroke is less just as it is with the upstroke and downstroke. This reduced range of motion seems to make using PC's a lot easier and people do seem to adapt much faster.

 

[coapman]

This reduced range of motion seems to make using PC's a lot easier and people do seem to adapt much faster.

That's the answer I needed, which means circular pedaling with shorter cranks is more efficient but sadly compared to mashing, it's not as effective.

 

[FrankDay]

That's the answer I needed, which means circular pedaling with shorter cranks is more efficient but sadly compared to mashing, it's not as effective.

Huh? What does this have to do with this "short cranks" thread, which I think is valid for both regular cranks and for PowerCranks and for mashers and spinners (although I suspect that spinners (those that spread the work out over most of the circle) will be able to go shorter than mashers (those that do all of the work on the down stroke). Let's try not to turn this into a PowerCranks thread.

 

[biopass]

Climbing is about power, not crank length. Crank length is accounted for when climbing through gearing. If you can generate a sustainable 350 watts on both 110 mm cranks and 175 mm cranks you should climb exactly the same as long as you are geared properly to be at the cadence necessary to allow you to generate the power. (You might even climb a little faster on the shorter cranks since they should weigh less.) If you aren't geared properly you aren't going to climb well regardless of how long your cranks are.

Man that made me laugh. Good joke

 

[coapman]

Huh? What does this have to do with this "short cranks" thread, which I think is valid for both regular cranks and for PowerCranks and for mashers and spinners (although I suspect that spinners (those that spread the work out over most of the circle) will be able to go shorter than mashers (those that do all of the work on the down stroke). Let's try not to turn this into a PowerCranks thread.

All that can be said about PC's has already been said, actually I was thinking about an earlier invention, the crank that continually changed length around the pedaling circle, longest for more leverage where pedal force and tangential effect is greatest and shortest for a more comfortable aero tt position in the most inefficient areas.

 

[Boeing]

Just a quick interjection: Has this thread surpassed the "should you wear team kits" thread for most redundancy?

carry on

 

[FrankDay]

All that can be said about PC's has already been said …

Really? The world is grateful that is off topic so will be allowed to die here.

 

[Boeing]

Crank arm length is awesome

 

[FrankDay]

For the interested I make this argument in a slightly different way in this recent article written for USA Cycling coaches newsletter (link is to a pdf copy)

Exploring Crank Length - Is Tradition Limiting Performance Gains

Comments and criticisms are, of course, welcomed by me.

 

[42x16ss]

Just a quick interjection: Has this thread surpassed the "should you wear team kits" thread for most redundancy?

carry on

Yes, I'd say it has. The only thing stopping it from having the most redundancy on the entire forum is the clinic

 

[FrankDay]

I have been working pretty hard the last week or two trying to figure out how to best explain this issue. I believe this is my best effort yet at explaining the principle I am trying to convey.

www.powercranks.com/assets/pdfs/aerodynamicmusings.pdf

I, again, look forward to any comments and/or criticisms.

 

[simo1733]

I have been working pretty hard the last week or two trying to figure out how to best explain this issue. I believe this is my best effort yet at explaining the principle I am trying to convey.

www.powercranks.com/assets/pdfs/aerodynamicmusings.pdf

I, again, look forward to any comments and/or criticisms.

Interesting article that does a good job of explaning the principle.In my own expierience I am definately more comfortable and faster on 170 than on 172.5 or 175s.I have never had the chance to try anything shorter than 170.
I don't think the angle of the Tri bars would be UCI compliant though.

 

[coapman]

I have been working pretty hard the last week or two trying to figure out how to best explain this issue. I believe this is my best effort yet at explaining the principle I am trying to convey.

www.powercranks.com/assets/pdfs/aerodynamicmusings.pdf

I, again, look forward to any comments and/or criticisms.

The distance a rider's leg has to travel with the longer 170 crank is of minor significance if you are a masher because he has only to concentrate and apply torque with each leg over 120 degrees of the pedaling circle or with the semi-circular style where concentration and torque application is required for 180 degrees. It is only the weaker style circular pedaler that has the inconvenience of attempting to concentrate and apply torque over the entire circle.

 

[coapman]

I have been working pretty hard the last week or two trying to figure out how to best explain this issue. I believe this is my best effort yet at explaining the principle I am trying to convey.

www.powercranks.com/assets/pdfs/aerodynamicmusings.pdf

I, again, look forward to any comments and/or criticisms.[/QUOT




With the recommended waist measurement of 94 cm (37") or below and a set of 'Scott Rake' clip on aero bars which are similar to riding in the drops, a rider should easily get to that 90mm crank body position while using the increased torque advantage of the longer 170 mm cranks.

 

[FrankDay]

With the recommended waist measurement of 94 cm (37") or below and a set of 'Scott Rake' clip on aero bars which are similar to riding in the drops, a rider should easily get to that 90mm crank body position while using the increased torque advantage of the longer 170 mm cranks.

Perhaps so but my thoughts are for those few who are unable to attain that position on standard cranks due to flexibility issues. Thanks for the feedback.

 

[FrankDay]

something to keep this thread alive a little (or lot) longer. Today I sent in a deposit to reserve some wind-tunnel time in mid-April to test the ideas in my paper and more.

I have an athlete who has been experimenting with different crank lengths and has tested himself the last 3 weekends at 145, 125, and 105 mm. He tells me he tested best at 105 but I don't have all the data yet. And, his coach wants to repeat the testing to be sure (and I want him to test even shorter since he apparently hasn't gone beyond his max yet). He has agreed to be the subject for these tests. With him we should be able to get a good sense of the effects of crank length on both aerodynamics and power and be able to then make some predictions as to the effect on speed. This should be fun for everyone who has an interest in this (or almost everyone anyhow).

 

[coapman]

something to keep this thread alive a little (or lot) longer. Today I sent in a deposit to reserve some wind-tunnel time in mid-April to test the ideas in my paper and more.

I have an athlete who has been experimenting with different crank lengths and has tested himself the last 3 weekends at 145, 125, and 105 mm. He tells me he tested best at 105 but I don't have all the data yet. And, his coach wants to repeat the testing to be sure (and I want him to test even shorter since he apparently hasn't gone beyond his max yet). He has agreed to be the subject for these tests. With him we should be able to get a good sense of the effects of crank length on both aerodynamics and power and be able to then make some predictions as to the effect on speed. This should be fun for everyone who has an interest in this (or almost everyone anyhow).

Are these your own PC type cranks, if not where do you get them. Would you agree that if you reduce your crank by 20 mm, while you lose a full 20 mm of leverage, you gain only part of this in the upper clearance. Also you should probably start by reducing pedal stack height and get the sole of your foot as close as is effectively comfortable to the pedal axle.

 

[FrankDay]

Are these your own PC type cranks, if not where do you get them.

Yes, these are specially drilled out PowerCranks to allow him to experiment with crank length in 20 mm increments. It would be more difficult (but not impossible) to do this experiment, I suppose, on regular cranks because it would require having a whole bunch of hard to find crank lengths to do the same.

Would you agree that if you reduce your crank by 20 mm, while you lose a full 20 mm of leverage, you gain only part of this in the upper clearance.

I do not have a clue what you are talking about when you say "you gain only part of this in the upper clearance". If you take 20 mm off the crank length you take 20 mm off the entire circle.

Also you should probably start by reducing pedal stack height and get the sole of your foot as close as is effectively comfortable to the pedal axle.

Again, what are you talking about here? What does this have to do with this crank length issue?

 

[coapman]

Yes, these are specially drilled out PowerCranks to allow him to experiment with crank length in 20 mm increments. It would be more difficult (but not impossible) to do this experiment, I suppose, on regular cranks because it would require having a whole bunch of hard to find crank lengths to do the same.
I do not have a clue what you are talking about when you say "you gain only part of this in the upper clearance". If you take 20 mm off the crank length you take 20 mm off the entire circle.
Again, what are you talking about here? What does this have to do with this crank length issue?

Could you explain exactly where and how you believe the shorter crank advantage takes effect.

 

[FrankDay]

Could you explain exactly where and how you believe the shorter crank advantage takes effect.

I think I have done this before but here goes.

1. Why does power increase? I believe the reasons are two main ones.

a. shorter cranks slow pedal speed, making it easier for the rider to apply more force to the pedal. The rider cannot apply any force to the pedal until he gets the foot up to pedal speed. The slower the pedal speed the sooner force can start to be applied.

b. A smaller range of motion keeps the hip and knee joints in a generally more efficient and powerfully leveraged angles such that any given muscle contractile force results in higher pedal force.

So, while it may take more force to generate any given power with shorter cranks, shorter cranks keep the legs in a more efficient configuration for applying force, making it easier to do so than when they are bent too much. Now, I guess I could be wrong here but something has to explain what was found by Martin and by those who are doing these experiments for me.

2. The aero advantages are easy to explain. Shorter cranks and higher saddle will reduce the frontal area presented to the wind. Did you download and read the essay I wrote on the subject? I think that illustrates this point very well.