The importance of crank length to the cyclist.

[CoachFergie]

Well I'm not claiming the unimportance of crank length because my riders cleaned up at NZ track cycling champs and Oceania Road Cycling Champs. Not even because one rider went from 165mm cranks to 172.5mm cranks and produced 30 watts more in his Kilo. I am not even claiming it's down to my coaching, maybe he wore his lucky red socks that night.

The evidence as supplied in the presentation by Martin is pretty clear cut. The only one who hasn't moved on is the person marketing short cranks.

 

[FrankDay]

Well I'm not claiming the unimportance of crank length because my riders cleaned up at NZ track cycling champs and Oceania Road Cycling Champs. Not even because one rider went from 165mm cranks to 172.5mm cranks and produced 30 watts more in his Kilo. I am not even claiming it's down to my coaching, maybe he wore his lucky red socks that night.

The evidence as supplied in the presentation by Martin is pretty clear cut. The only one who hasn't moved on is the person marketing short cranks.

Hey Fergie, In a few weeks I have some wind tunnel time in which I am going to measure the effects of crank length alone on aerodynamic drag. Why don't you tell us what you predict we will find? Assuming there is an aerodynamic benefit to going to shorter cranks, does it ever stop? What will the shape of the curve look like as we go from 170 shorter, keeping everything else (except seat height) the same? If there is an affect, how big will the maximum effect be? Those are the main questions I am going to try to answer. Give us your predictions now.

Others, of course, are welcome to place their guesses now. If there is enough interest maybe I should come up with a prize. If we get enough guesses, I will come up with something.

 

[CoachFergie]

I predict you will be able to put your subjects in whatever position you want to show what you want to show. That's what I have found spending time in the wind tunnel. Whether those positions are ridable or riders can produce sustained power in those positions is another question.

 

[Semper Fidelis]

Hey Fergie, In a few weeks I have some wind tunnel time in which I am going to measure the effects of crank length alone on aerodynamic drag. Why don't you tell us what you predict we will find? Assuming there is an aerodynamic benefit to going to shorter cranks, does it ever stop? What will the shape of the curve look like as we go from 170 shorter, keeping everything else (except seat height) the same? If there is an affect, how big will the maximum effect be? Those are the main questions I am going to try to answer. Give us your predictions now.

Others, of course, are welcome to place their guesses now. If there is enough interest maybe I should come up with a prize. If we get enough guesses, I will come up with something.

Don't go messing with the seat heights. Keep it at the same setting.

 

[FrankDay]

Don't go messing with the seat heights. Keep it at the same setting.

Ugh, if you don't "mess" with seat height then the "fit" goes to pot, power will probably drop, and there is zero benefit to going shorter. The intent is to keep leg extension the same at BDC, in other words, a "proper" (or, at least, a similar) fit for power production at the various crank lengths.

Anyhow, that is what we will be doing. Put your guess in now.

 

[FrankDay]

I predict you will be able to put your subjects in whatever position you want to show what you want to show. That's what I have found spending time in the wind tunnel. Whether those positions are ridable or riders can produce sustained power in those positions is another question.

We are not "putting them in any position to show what we want to show". All we are going to do is start out with a certain crank length and saddle and handlebar height and then change crank length and saddle height (leaving handlebar height constant), as I did in the essay I wrote on this and linked to earlier, and measure the difference in drag. I am not trying to "show" anything. I am trying to find out how big a difference is seen, if any. Make your prediction.

 

[42x16ss]

We are not "putting them in any position to show what we want to show". All we are going to do is start out with a certain crank length and saddle and handlebar height and then change crank length and saddle height (leaving handlebar height constant), as I did in the essay I wrote on this and linked to earlier, and measure the difference in drag. I am not trying to "show" anything. I am trying to find out how big a difference is seen, if any. Make your prediction.

My prediction is that the gain - if any - will be less than what your athletes would see if you put as much time and energy into making them stronger, better bike riders...

 

[coapman]

We are not "putting them in any position to show what we want to show". All we are going to do is start out with a certain crank length and saddle and handlebar height and then change crank length and saddle height (leaving handlebar height constant), as I did in the essay I wrote on this and linked to earlier, and measure the difference in drag. I am not trying to "show" anything. I am trying to find out how big a difference is seen, if any. Make your prediction.

In each position check their max speed at the end of a 15 second sprint attempt.

 

[CoachFergie]

My prediction is you will be able to put them into a position that shows whatever suits the marketing of short cranks. For me the wind tunnel is only one part of the performance process and once I have an aerodynamic position in the lab the next step is down to the track to test if a rider can produce sustained power in that position or perform a Chung Test to determine if a real world advantage exists.

 

[Semper Fidelis]

Ugh, if you don't "mess" with seat height then the "fit" goes to pot, power will probably drop, and there is zero benefit to going shorter. The intent is to keep leg extension the same at BDC, in other words, a "proper" (or, at least, a similar) fit for power production at the various crank lengths.

Anyhow, that is what we will be doing. Put your guess in now.

What type of climbs, descents, turns, flats, and weather conditions will you have with this experiment?

 

[FrankDay]

What type of climbs, descents, turns, flats, and weather conditions will you have with this experiment?

I guess you are referring to this short crank experiment, not the wind tunnel experiment I most recently referred to.

We did have one rider come in top 10 overall at Everest challenge (28k ft climbing) last year riding on 110 mm cranks. Does that count as a "type of climb"?

And here is a picture of a bike with 125 mm cranks with a 22.5 cm drop that the rider referred to as being "super comfy". He has subsequently moved on to now preferring 105 mm cranks which will give him a 24.5 cm drop and his power tested higher at this length than 125. https://fbcdn-sphotos-a.akamaihd.net/hphotos-ak-ash3/546831_10151458896440204_665020203_23769217_212586518_n.jpg
Anyhow, does it really matter? It either works or it doesn't. Many who try it seem to like the change. Those who don't try it usually think it stupid. I am hoping to have some better data soon to add to the debate.

 

[CoachFergie]

And here is a picture of a bike with 125 mm cranks with a 22.5 cm drop that the rider referred to as being "super comfy". He has subsequently moved on to now preferring 105 mm cranks which will give him a 24.5 cm drop and his power tested higher at this length than 125. I am hoping to have some better data soon to add to the debate.

What was the test? Yes, some data would make a change

 

[coapman]

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

Shoe/pedal stack heights (higher and lower) will have the same effect as longer and shorter cranks at the top 12 o'c position of the pedaling circle.

 

[42x16ss]

I guess you are referring to this short crank experiment, not the wind tunnel experiment I most recently referred to.

We did have one rider come in top 10 overall at Everest challenge (28k ft climbing) last year riding on 110 mm cranks. Does that count as a "type of climb"?

And here is a picture of a bike with 125 mm cranks with a 22.5 cm drop that the rider referred to as being "super comfy". He has subsequently moved on to now preferring 105 mm cranks which will give him a 24.5 cm drop and his power tested higher at this length than 125. https://fbcdn-sphotos-a.akamaihd.net/hphotos-ak-ash3/546831_10151458896440204_665020203_23769217_212586518_n.jpg
Anyhow, does it really matter? It either works or it doesn't. Many who try it seem to like the change. Those who don't try it usually think it stupid. I am hoping to have some better data soon to add to the debate.

As Fergie said some data would be refreshing. As would a setup used on a race bike, not a commuter like the one shown.

 

[CoachFergie]

As Fergie said some data would be refreshing. As would a setup used on a race bike, not a commuter like the one shown.

Also aerodynamics in the wind tunnel has little relevance to performance. It's only one part of the performance testing process. Liguigas did testing in the wind tunnel, then on the track then out on the road to perfect their riders positions. That way you ensure you can generate power in a position and sustain it for the goal race duration.

 

[Zam_Olyas]

Also aerodynamics in the wind tunnel has little relevance to performance. It's only one part of the performance testing process. Liguigas did testing in the wind tunnel, then on the track then out on the road to perfect their riders positions. That way you ensure you can generate power in a position and sustain it for the goal race duration.

Do you have anyone riding at melbourne track world championship?

 

[CoachFergie]

Alex Frame was part of the Track Cycling Development I ran in Canterbury in 2007. 4th in the Scratch Race.

175mm track cranks btw.

 

[FrankDay]

42 and Fergie, you guys just kill me.

42, you don't seem to understand what is trying to be done. The goal is to measure the effect of rider position on the bike, especially as it relates to crank length. The bike the rider is on during this test is immaterial to this task.

And, Fergie, it just seems you are putting forth the conditions now by which you will be able to bash the results (somewhat similar to what 42 is doing).

Anyhow, the results will be the results. Why don't both of you wait to see them before you start bashing them.

And, it seems no one wants to predict the results. I will wait until next week but I will predict what I think we will (or could) find. Then, we will all see whether I am correct or not.

 

[coapman]

42 and Fergie, you guys just kill me.

42, you don't seem to understand what is trying to be done. The goal is to measure the effect of rider position on the bike, especially as it relates to crank length. The bike the rider is on during this test is immaterial to this task.

And, Fergie, it just seems you are putting forth the conditions now by which you will be able to bash the results (somewhat similar to what 42 is doing).

Anyhow, the results will be the results. Why don't both of you wait to see them before you start bashing them.

And, it seems no one wants to predict the results. I will wait until next week but I will predict what I think we will (or could) find. Then, we will all see whether I am correct or not.

I agree, the bike is immaterial but what exactly are your objectives in doing this test, is it the trail of smoke that moves over the rider and how it reacts to the different positions. What are we expected to predict ?

 

[CoachFergie]

42 and Fergie, you guys just kill me.

42, you don't seem to understand what is trying to be done. The goal is to measure the effect of rider position on the bike, especially as it relates to crank length. The bike the rider is on during this test is immaterial to this task.

And, Fergie, it just seems you are putting forth the conditions now by which you will be able to bash the results (somewhat similar to what 42 is doing).

Anyhow, the results will be the results. Why don't both of you wait to see them before you start bashing them.

And, it seems no one wants to predict the results. I will wait until next week but I will predict what I think we will (or could) find. Then, we will all see whether I am correct or not.

All you are doing is stroking your own confirmation bias. The results will have no real world meaning.

 

[CoachFergie]

I agree, the bike is immaterial but what exactly are your objectives in doing this test, is it the trail of smoke that moves over the rider and how it reacts to the different positions. What are we expected to predict ?

A change in drag. But because each change in crank length requires a change in seat and handlebar position the study will not show data will not show anything conclusive.

The only smoke will be that associated with mirrors.

 

[42x16ss]

Anyhow, the results will be the results. Why don't both of you wait to see them before you start bashing them.

Ok, just one question - WHERE ARE THEY????

 

[coapman]

A change in drag. But because each change in crank length requires a change in seat and handlebar position the study will not show data will not show anything conclusive.

The only smoke will be that associated with mirrors.

Thanks CoachFergie, now I get it. These minor details are taken care of by the perfect TT technique which uses the longest crank within a rider's comfort zone and still gives an ideal aero position by using plantar flexion to extend effective leg length around 5 o'c and dorsi flexion to shorten it around the start of the power stroke at 11 o'c.

 

[Tapeworm]

Alex Frame was part of the Track Cycling Development I ran in Canterbury in 2007. 4th in the Scratch Race.

175mm track cranks btw.

If he'd run 125mm cranks he would have won! The dude's ancedote with the fixxxie commuter is proof of this

 

[FrankDay]

What are we expected to predict ?

I thought the question was pretty straight forward but I guess not so, I guess, you could start with this simple question: How will the drag change as the crank length (and associated seat height), and nothing else - including handlebar height, changes. To put it another way, how will the drag of the rider change as the height of the head changes compared to the height of the rear end. Now, I intend to ask some other questions also but I think that is enough for this thread right now.