The importance of crank length to the cyclist.

[CoachFergie]

So, let me get this straight. You do believe that shorter cranks could help improve overall aerodynamics but you do not believe they could help improve the overall power/aerodynamics tradeoff? Is that correct?

One can improve aerodynamics but this can come at the cost of power delivery.

And there are less costly methods of improving aerodynamics.

 

[FrankDay]

One can improve aerodynamics but this can come at the cost of power delivery.

And there are less costly methods of improving aerodynamics.

Answer the question. Are you saying that shorter cranks do not have the potential to improve the overall power/aerodynamic equation for a rider. Forget the cost. Forget that other methods also exist. Answer the question, do they have that potential?

 

[blutto]

...just a series of silly little questions...and bear with me here as this will lead back to the OP...

...when someone is being set up on a bike for the most efficient power output how important is the seat to pedal height at TDC and at BDC ( all relative to the seat centre/bottom bracket centre axis line)....are the two related?...is one vastly more important than the other?...can one be safely ignored?....can both be safely ignored.....and for any/all of the answers for the above questions you may care to answer an explanation for your answer would be appreciated ( and explanations can be an educated guess and does not have to be detailed or long )...

Cheers

blutto

 

[onetrack]

no loss in power (as recorded by a power meter not my imagination).

This doesn't prove which of the 10,000 variables didn't result in a loss in power as recorded by a power meter.

 

[CoachFergie]

I didn't say what affects power.

No Frank at this stage there is no evidence that a short crank will optimise power.

This doesn't prove which of the 10,000 variables didn't result in a loss in power as recorded by a power meter.

 

[Alex Simmons/RST]

For Frank's benefit, shortening cranks is an option (so is everything really, like longer cranks*). It's not the option I would place high on the priority list when examining performance improvement options for most individuals but it's an option.

But when examining crank length and/or position changes, they must be demonstrated to conclusively improve performance. This would be done by field testing with a power meter, such that you not only determined what aero benefit there was, but also what impact there is on power - under actual riding conditions.

Of course in Frank's world, he prefers the logical fallacy known as an Appeal to Consequence, and so using a power meter in this manner to actually prove something is an anathema to that.

I do note that for some of my riders, there is no potential to lower their front end further as it is (or more correctly, going lower than they are doesn't improve their aerodynamics) and hence using shorter cranks may just end up lifting their saddle and making the aero outcome worse (which is what I found with one rider on the track).

IOW, what is right for any individual, is, well, individual, and needs to be validated with proper testing using appropriate equipment and test methodologies. Anecdotal reports really serve no purpose for this.


* I note that for one client a few years ago, we attained a better power to aero drag ratio when he lengthened his cranks to 180mm (from 170mm). Go figure, eh?

 

[FrankDay]

For Frank's benefit, shortening cranks is an option (so is everything really, like longer cranks*). It's not the option I would place high on the priority list when examining performance improvement options for most individuals but it's an option.

That wasn't that hard was it?

But when examining crank length and/or position changes, they must be demonstrated to conclusively improve performance. This would be done by field testing with a power meter, such that you not only determined what aero benefit there was, but also what impact there is on power - under actual riding conditions.

Well, we agree field testing must be done although it is not clar to me that a PM is the only way to do this testing. Why is it necessary to keep bringing the PM up in these discussions?

Of course in Frank's world, he prefers the logical fallacy known as an Appeal to Consequence, and so using a power meter in this manner to actually prove something is an anathema to that.

LOL. So, it is fallacious to "appeal" to the possibility of racing faster if one doesn't have a PM to prove the outcome. It is a wonder we ever learned how to ride a bicycle before the days of the PM or ever thought one might be able to ride faster than another without this wondrous instrument.

I do note that for some of my riders, there is no potential to lower their front end further as it is (or more correctly, going lower than they are doesn't improve their aerodynamics) and hence using shorter cranks may just end up lifting their saddle and making the aero outcome worse (which is what I found with one rider on the track).

Really? You have riders that have zero potential to lower their front end? And, if they did their drag would increase? And, you know this without trying? How?

IOW, what is right for any individual, is, well, individual, and needs to be validated with proper testing using appropriate equipment and test methodologies. Anecdotal reports really serve no purpose for this.

Well, anecdotal reports do serve a purpose if they get one to try this for themselves and they find they test better with the change. Don't you think? And, they do serve a purpose if they cause some scientist to do a study and the hypothesis is confirmed, don't you think?

* I note that for one client a few years ago, we attained a better power to aero drag ratio when he lengthened his cranks to 180mm (from 170mm). Go figure, eh?

I would be curious to hear the details of the fit change. Do you have pictures of the before and after. Is that the only change made?

 

[CoachFergie]

Well, we agree field testing must be done although it is not clar to me that a PM is the only way to do this testing. Why is it necessary to keep bringing the PM up in these discussions?

Valid and reliable measure of performance.

LOL. So, it is fallacious to "appeal" to the possibility of racing faster if one doesn't have a PM to prove the outcome.

A power meter doesn't record outcomes.

It is a wonder we ever learned how to ride a bicycle before the days of the PM or ever thought one might be able to ride faster than another without this wondrous instrument.

A power meter doesn't teach you how to ride a bike.

Really? You have riders that have zero potential to lower their front end?

Yup we have riders we have taken into the wind tunnel and we can't get them any more aero. Perfect shape and super flexibility.

Well, anecdotal reports do serve a purpose if they get one to try this for themselves and they find they test better with the change. Don't you think? And, they do serve a purpose if they cause some scientist to do a study and the hypothesis is confirmed, don't you think?

A scientist has studied various crank length so we don't need to test this for ourselves.

 

[Alex Simmons/RST]

Well, we agree field testing must be done although it is not clar to me that a PM is the only way to do this testing. Why is it necessary to keep bringing the PM up in these discussions?

What is your proposed alternative to testing these things under race like conditions? An endless supply of wind tunnel time perhaps?

So, it is fallacious to "appeal" to the possibility of racing faster if one doesn't have a PM to prove the outcome. It is a wonder we ever learned how to ride a bicycle before the days of the PM or ever thought one might be able to ride faster than another without this wondrous instrument.

Strawman, nobody said that.

Really? You have riders that have zero potential to lower their front end? And, if they did their drag would increase? And, you know this without trying? How?

Re-read what I wrote. I said that lowering their front end further isn't improving their aerodynamics. Some are low enough.

e.g. should this rider go lower?

Well, anecdotal reports do serve a purpose if they get one to try this for themselves and they find they test better with the change. Don't you think? And, they do serve a purpose if they cause some scientist to do a study and the hypothesis is confirmed, don't you think?

Sure, which is perhaps why it has been done. Can't help it if you choose to ignore it.

I would be curious to hear the details of the fit change. Do you have pictures of the before and after. Is that the only change made?

I am not at liberty to do that. Saddle was lowered with the increase in crank length.

 

[blutto]

Of course in Frank's world, he prefers the logical fallacy known as an Appeal to Consequence, and so using a power meter in this manner to actually prove something is an anathema to that.

...would be very careful if I were you when throwing that particular term around...its a very slippery boogger....and I would, in another time and place, argue that its use in this particular instance is much more wrong than right...

Cheers

blutto

 

[onetrack]

e.g. should this rider go lower?

The questions I have is, at that crank length, can this rider go lower. If not, What effect would it have. Would he be able to produce more power? Would it be more comfortable? Would his endurance improve? If his hip wasn't as cramped at tdc would air flow around him better?

a scientific study won't prove anything for him, putting short cranks on HIS bike and measuring HIS wattage with short cranks then measuring HIS drag coefficient would mean something. But only for him.

 

[Martin318is]

The questions I have is, at that crank length, can this rider go lower. If not, What effect would it have. Would he be able to produce more power? Would it be more comfortable? Would his endurance improve? If his hip wasn't as cramped at tdc would air flow around him better?

a scientific study won't prove anything for him, putting short cranks on HIS bike and measuring HIS wattage with short cranks then measuring HIS drag coefficient would mean something. But only for him.

I think that is the point that most of us have been trying to make. put them on but do the testing before keeping them permanently. Most of us oud take that personal attitude even if there were scientific evidence - just because it works in general doesn't mean it will work for me. Test it and see

 

[FrankDay]

What is your proposed alternative to testing these things under race like conditions? An endless supply of wind tunnel time perhaps?

There are plenty of inexpensive options. Repeat closed course time-trials under light wind conditions works pretty well.

Re-read what I wrote. I said that lowering their front end further isn't improving their aerodynamics. Some are low enough.

e.g. should this rider go lower?

Well, I have commented on this photo before. While I do think his position could be improved slightly, and lower might make a small difference in his aerodynamics I am more concerned about what that position is doing to his power. (I assume you have a PM, have you measured what this position is costing him power-wise?) It is impossible, AFAIK, to anyone to get their knee that close to their chest without pushing it up there (and he isn't even at the closest point yet). The work required to get his knee that high has to be robbing from the work that could be going to the wheel. So, IMHO, the major benefit this rider is likely to see from trying shorter cranks is improved power output, not improved aerodynamics, because shorter cranks will move the knee away from the chest even though the seat is move higher.

 

[FrankDay]

Sure, which is perhaps why it has been done. Can't help it if you choose to ignore it.

Perhaps you could point me to the study I am choosing to ignore.

I am not at liberty to do that. Saddle was lowered with the increase in crank length.

In other words, "trust me".

 

[onetrack]

I think that is the point that most of us have been trying to make. put them on but do the testing before keeping them permanently. Most of us oud take that personal attitude even if there were scientific evidence - just because it works in general doesn't mean it will work for me. Test it and see

This is definitely the point I've been trying to make. Apparently poorly articulating it. Not sure why some people are asking me to point out a scientific study when I am simply sharing my experience with this change.


One thing jumps out at me looking at that picture. Look at the riders pelvic rotation compared to the curve of his spine. Why is he holding his pelvis like that while contorting his spine to reach the handlebar? likely it is because this is the only way to ride so aggressively without your thighs crashing into your ribs luckily for him, he is flexible. Now if we shorten the cranks which raises the seat while lowering the foot at tdc his hips can rotate forward eliminating the need for an extreme bend in his spine. This also creates the potential for higher efficiency and power as we lessen the wasteful over the top part of the pedal stroke, and allowing the hip flexors to contribute more. Maybe getting rid of this extreme bend in the rider's spine will allow his body to be less jarred by variations in road surface thus allowing a smoother faster more comfortable ride. a race tire effect.

 

[oldborn]

Can agree with onetrack.
Ride and let ride

 

[Alex Simmons/RST]

My point are:

1. not everyone needs short cranks to get low/aero (but it is an option to consider, like many things)

2. going lower is not always more aero (or faster) anyway

3. test it properly. tests that are not tunnel or power meter based simply do not have the level of precision required. anything else is simply guesstimation and unreliable

 

[Oldman]

What on earth does this thread have to do with my product other than we offer the option for the user to experiment with this while also learning how to pedal in the PC fashion (which I think is a separate benefit)? The potential benefits of shorter cranks should accrue to anyone, whether they are a PC'er or not. And, this experiment doesn't have to cost an arm and a leg - C. Ogden won IM Western Australia on 145mm cranks he picked up off the internet for $22. It might be that a PC'er might be able to go shorter than a non-PC'er but that is speculation on my part.

I have trained with too many State Champion TTers, National Champion TTers, Masters Worlds Champ TTers, Masters Worlds Champ Pursuiters, Masters Pursuit World Record Holders and Pro TTers of podium level to encourage anyone to pursue your protocol. Most of these guys/gals have been in a wind tunnel and I know a few aerospace engineers.
The thread seemingly has to do with your product on the occasions you offer up anecdotal evidence of a random customer improving his time over their previous "efforts". "Efforts" are in quotes because most of the time you are relying on their statement of improvement.

Having participated with or having witnessed some of the performances above my anecdotal evidence would seem more compelling; would it not?

 

[Oldman]

My point are:

1. not everyone needs short cranks to get low/aero (but it is an option to consider, like many things)

2. going lower is not always more aero (or faster) anyway

3. test it properly. tests that are not tunnel or power meter based simply do not have the level of precision required. anything else is simply guesstimation and unreliable

And isn't FASTER the point that Mr. Frank is missing?

 

[Oldman]

And isn't FASTER the point that Mr. Frank is missing?

By the way...I saw a Delorean driving around today. It looked both lower, aero and fast. It was not one of the three...

 

[FrankDay]

Having participated with or having witnessed some of the performances above my anecdotal evidence would seem more compelling; would it not?

I guess it is to you. I have no problem with that. Do whatever you feel is best. If my ideas don't interest you then I suggest you ignore them.

 

[FrankDay]

My point are:

1. not everyone needs short cranks to get low/aero (but it is an option to consider, like many things)

Well, your picture certainly shows one can get pretty aero if one is scrunched up pretty well.

2. going lower is not always more aero (or faster) anyway

Have you ever considered that it may not be FASTER because so much power is being lost trying to get aero, due to the scrunching.

3. test it properly. tests that are not tunnel or power meter based simply do not have the level of precision required. anything else is simply guesstimation and unreliable

You never did answer the question as to how much power your rider was losing being so closed up? You are the PM guy. Are you telling me you haven't measured it?

You and Fergie (and a few others) seem to be missing the entire point of my first post. Short cranks, from my theorizing and our experimenting seem allow the rider to achieve a much lower and more aerodynamic position without losing much, if any, power. So, we would expect the change to be faster. Of course, if one isn't willing to experiment one will never know will one?

Oh, and I am still waiting for you to inform me about those studies that you say have been done that you seem to think I am ignoring.

 

[FrankDay]

By the way...I saw a Delorean driving around today. It looked both lower, aero and fast. It was not one of the three...

What engine does the Delorean have? Would you rather have a Yugo with a Ferarri engine or a Ferarri with a Yugo engine? But, to be really fast, you need a Ferarri with a Ferarri engine.

 

[FrankDay]

And isn't FASTER the point that Mr. Frank is missing?

No, that is the point CoachFergie[*] seems to miss. He is the one equating performance with power.

[*] = edited by mod

 

[Martin318is]

And isn't FASTER the point that Mr. Frank is missing?

read it again:

2. going lower is not always more aero (or faster) anyway

he is saying that both that being low is not always more aero and he is ALSO saying that being low is not always faster.