Paging Zakeen re: Crank Length

[TheKaiser]

Just stumbled across this GCN video which looks at pro's choice of crank arm length and has a short clip of Adam Hansen (AKA Zakeen) talking about his use of 180mm cranks:
https://www.youtube.com/watch?v=bjrNuPjACnU

I have always liked Hansen's attention to tech detail, and I love and admire his homemade shoes, but his explanation for why he uses 180s seems incredibly simplistic for a man of his brilliance. In it, he basically says its simply because longer cranks give you more leverage, ignoring the fact that you can alter the drivetrain system's leverage with gearing changes as well, and ignoring any biomechanical advantage/disadvantage of a longer crank. Maybe he is just trying to throw everyone off the scent, or maybe he is kidding around, or maybe it is out of context, but it is the kind of explanation I would expect from a forum buffoon, not an insightful pro rider/tech wizard.

If you don't follow the issue here, and if you can stomach Youtube comments, scroll down to the thread started by Nick Kukoreko, and then look toward the bottom of the 90ish comments for the Maxz and tom morris posts, which explain the issue quite lucidly.

So, Zakeen, can you pull yourself away from your long hours of being a Protour hardman and take a minute or two to fill us in? And if you have any extra time, how about a step-by-step how-to to help guide us would-be DIY carbon shoe builders?

[Valbrona]

You miss the point with pros/serious amateur racers. Many are fully aware of the science and the move to shorter cranks, but instead choose to trial different lengths and select the length that best suits their pedalling style. As simple as that.

[Hexsense]

myself at 5'6.5 (169cm) using 165mm crank which the crank is proportionally longer than
Adam Hansen at 6'1 (1.86 m) using 180mm crank. (i need to be 170.5 using 165mm crank to get the same ratio as him, if we only talking about height without inseam).

For me, people ask why i use crank so short.
For Adam, people ask why he use crank so long.
Not fair.

[AJS914]

I'm 6 foot and using 170s or 172.5s now. The fact is that there isn't a huge difference between the stock crank lengths. 6% between 170s and 180s. If he likes 180s and can turn them at 100 rpms then so be it. They aren't making him slower.

http://pelotonmagazine.com/travel-cultu ... am-hansen/

[Mr.Gib]

The way I look at it, is that if the longer crank doesn't reduce your biomechanical efficiency, then indeed it does give you the ability to apply more force at the axel. In other words one should use the longest crank that one can turn efficiently. This is theoretical of course. In practice when low cadence power is called for I wish I had long cranks, and when high cadence in needed I would rather be on short cranks.

[TheKaiser]

You miss the point with pros/serious amateur racers. Many are fully aware of the science and the move to shorter cranks, but instead choose to trial different lengths and select the length that best suits their pedalling style. As simple as that.

Well if he has trialed them all and tests better for power or endurance with 180s, then he should of course be using them, and I am in total agreement with you. My point was simply that the rational he quite elaborately states for using 180s in the video mentions nothing of his own testing and is based purely on a mechanical explanation of lever length. In the video he says he consulted a mechanical engineer who told him a longer lever requires less torque, which everyone who has ever dealt with breaking free a frozen bolt knows, and that is why he uses 180s. It disregards both the principles of physics that basically state "you can't get something for nothing" and the principles of biomechanics that suggest you need to take into account your bodies response to the different range of motion. If longer levers were truly always superior in this application, then he should throw together some custom carbon 200mm or 225mm cranks. If that's too much work, he could order some off the shelf from Zinn cycles.

[TheKaiser]

The way I look at it, is that if the longer crank doesn't reduce you biomechanical efficiency, then indeed it does give you the ability to apply more force at the axel. In other words one should use the longest crank that one can turn efficiently. This is theoretical of course. In practice when low cadence power is called for I wish I had long cranks, and when high cadence in needed I would rather be on short cranks.

If the gear ratio and cadence was fixed, then you are correct, like if you have run out of gears on a crazy steep uphill or long straight descent. But in those scenarios you mention, you are basically using a change in crank length as a proxy for having the ability to shift to a more appropriate gear.

In exchange for the greater leverage that the longer crank offers, it requires your feet to trace a larger circle, which, for a given cadence, means your feet need to go faster. It is basically increasing the mechanical advantage that your feet have over the rear tire contact patch.

In a road racing context where you are on a multi speed bike and haven't run out of gears, cadence is variable, and that same increase in mechanical advantage can also be achieved simply by shifting to a lower gear and spinning a faster cadence. It will also require an increase in foot speed, and will also increase the mechanical advantage your feet have over the rear tire contact patch.

The relationship between linear foot speed and mechanical advantage over the rear tire contact patch will be identical for a longer crank & higher gear vs. a shorter crank & lower gear.

For those reasons, I think that one should use the most biomechanically efficient crank length for you, and then adjust mechanical advantage as needed with gearing. If you frequently find yourself running out of gears and wishing for a long crank for low cadence power, or a short crank for high cadence spinning, then swapping out to a wider range cassette/rings would be in order.

[11.4]

A conversation with a pro doesn't have an awful lot of relevance for the average rider here. Hansen also may not have addressed all the factors that went into his decision, plus he's a bit of an outlier in many ways in the peloton. But since this has been discussed a hundred times here, let's recap a few points that bear on this decision:

1. If a long crank means your thighs are compressing your diaphragm, you are losing lung capacity and almost certainly need to change crank length. If you have the body geometry such that you can ride longer cranks without interference, that can also bear on your decision.
2. One's ability to rotate the hips defines the range of crank arm lengths one can use. As soon as hip impingement occurs or even flexibility limits are reached, you have to think about reducing crank arm length.
3. Remember that the tibia/fibia basically move up and down vertically, but the magnitude of that movement is driven entirely by the length of the femur. (There's a small contribution, plus or minus, from foot size or ankle flexion, but small relative to femur length.) If your femur is proportionately shorter, you can be tall but not take a long crank arm easily. Pro riders tend to have proportionately long femurs because the kinesiology of muscle contraction across a long femur allows for more power generation in most (but not all cases), so slightly longer crankarms can make sense for these more genetically gifted riders.
4. Next, remember that different riders will have different body geometries, so that one rider's femur may cover a very different range of angles (relative to horizontal) compared to another rider's. If your hips are farther back and your knee joint angle with the pedal at 12 o'clock is less, you may use a longer crank more effectively than a rider who sits farther forward and raises the thigh closer to horizontal. In short, positioning on a bike, even with the same basic fit, can drive a different crank arm length.

We also get into issues that even pros deal with, such as basic flexibility, hip anomalies that lead to hip impingement, knee tolerance and pain, things like heel spurs that limit ankle movement, and so on and so on. In the end there's a range of crank arm lengths that can work for any particular rider. For some riders it's a broad range; for other riders, it's quite narrow. So your real goal is to define your effective range and then, within that range, test to determine your best power output.

[cyclespeed]

Fully agree with TheKaiser and good points from 11.4 too.

Extra torque from longer cranks = extra torque from higher gear. (In one of my vids I present the force equations for this, from end of crank through the drivetrain to the tyre contact patch).

Shorter cranks demand less from the body; lower foot speeds, less straining of joints, less compression of torso.

But your morphology will play an important role, and long-legged, long femured riders may well be happier on slightier longer cranks than other riders of the same height.

Generally though, I get the impression that many riders would benefit from going to shorter cranks.

[KWalker]

I tried all sorts of fit and crank solutions last year to deal with issues caused by a hip impingement. The more complicated factor was that if I wanted even a remotely similar setup on the mtb then I was stuck with basically 2, maybe 3 length choices.

In the end the crank length made less of a difference than overall saddle position and it came down to preference. My cadence got a bit too high with the shorter cranks and felt a bit awkward while standing which became an issue on the MTB.

For me, riding longer cranks also comes with a further forward saddle position and more aft cleat position, both of which already open the hips. Both of these changes were made before changing crank lengths, not to facilitate a specific length

[11.4]

Shorter cranks demand less from the body; lower foot speeds, less straining of joints, less compression of torso.

Generally though, I get the impression that many riders would benefit from going to shorter cranks.

That's generally why many riders, both pro and otherwise, are going to shorter cranks. The old crank arm length arguments are one of many fictions dating back to the old CONI manuals of the 1950s. We've moved far beyond that and those old arbitrary standards have finally begun to fade away. It doesn't mean that a long crank arm isn't appropriate for a particular rider, just that there's a lot more going into the equation than just height or overall leg length. We're all experiments of one and our first job as cyclists is to figure out how our own body really works and how best to set up a bike around it. That's not necessarily a fitter's job or competence. When we're talking about feelings of flexibility, balance, tendency to tire, diaphragm impingement, and so on, you learn about these with miles in the saddle and that's really the only place to find it. And someone else's experience or expertise is really not likely to be all that relevant.

[AJS914]

Longer cranks also helped 30 years ago when pros (and everybody else) slogged up climbs at 60 rpms with their corncob cassettes.

[Johnny Rad]

...but his explanation for why he uses 180s seems incredibly simplistic for a man of his brilliance. I

I wonder if Adam Hansen just didn't want to delve into the crank length subject. He could've been bored with the question, interviewer or interview itself! Makes me think of Peter Sagan a few days ago when he could hardly be bothered to answer an interviewer why he came in 2nd at Omloop Het Nieuwsblad.

myself at 5'6.5 (169cm) using 165mm crank which the crank is proportionally longer than Adam Hansen at 6'1 (1.86 m) using 180mm crank. (i need to be 170.5 using 165mm crank to get the same ratio as him, if we only talking about height without inseam).

Hadn't thought of it in this way - nicely done. In other words, you and I are getting more leverage out of our proportionally longer can arms. We're monsters!

The fact is that there isn't a huge difference between the stock crank lengths. 6% between 170s and 180s.

This I've been aware of for some time, but your point bears mentioning again. Some folks can feel a mm of difference in their set-up somewhere whereas others just don't.


What's it all mean to me?! Well, I'm sticking with my 170mm crank arms because they seem to work well enough. If I had the time and money, I'd be open to experimenting with different lengths just to see what happens. Until then, I'm in the "don't fix what ain't broke" camp. Your mileage may vary, of course!

[zakeen]

So, Zakeen, can you pull yourself away from your long hours of being a Protour hardman and take a minute or two to fill us in? And if you have any extra time, how about a step-by-step how-to to help guide us would-be DIY carbon shoe builders?

I dont like to say to much, so you are right in that way

But to say a few things I disagree of, which does not mean I am correct, I watched your video Cyclespeed and your points on why its better to have shorter cranks were:

Leg doesn't come up so high so you can get your torso lower just by having shorter cranks.

This has nothing to do with crank length, I run super long. Then I ride a frame a little smaller then I should, but I must do that so I can have a shorter steering tube, meaning my stem, without spacing is as low as possible and then I still have a negative angled stem. If I ran the a bigger frame then I wouldnt be able to get my handle bars so low(bigger frame bigger steering tube). So having said all this. I really have an extreme low bars and still my legs dont hit my torso. I did however move my saddle more forwards which opens up my hip flexors and tilled down my saddle which helped even more.

Cornering, you have less ground clearance.

Im able to race without this problem.

To get maximum power is hard and fast peddling and its easier to maintain that on shorter cranks because you said it is a lot easier to maintain that circle of high speed circle. If you don't have to do a great big circle with longer cranks which is putting a lot more strain on your joints

This gets more interesting. Power output is Watts equals RPM X Torque. So having a longer crank arm requires less Torque/strain( which I believe is better for your joints ). Doing smaller circles to maintain higher speed I disagree a little. Legs are going up and down, like pistons in a engine. Every time they go up, stop and down they lose energy and the muscle has to re-fire again. I feel its easier to maintain a larger circle.

You mentioned that if a shorter crank does a 12 to 6 oclock rotation then the wheel travels the same as a longer crank doing the same. Then you say that people with longer cranks are using less force(which is the whole idea), saving energy and must be good.... on that rotation. Then you say: But no its just a simple question of gearing, because all you have to do for the shorter crank feel easier again is just change up a gear. The shorter crank becomes easier and you are back to the same thing and you have no advantage of having a longer crank.

This is where I think you are wrong. If you are at the same place by simply changing up the gear, then yes you are right, the amount of force would be the same for the smaller crank to do that 12 to 6oclock rotation in a smaller gear compare to the longer crank in a bigger gear. Force might be the same(depending on gearing differences). However, the wheel rotates far longer in a bigger gear then in a smaller gear. So you yourself say right there, that there is a difference. Same force, different crank length, different gearing's. But one gearing has a longer rollout would mean that difference in rollout is the advantage of longer cranks. You would rider further with the same force applied on the crank.

Now I know its not as simple as that, but yourself there says it.

How I got to my crank length were pretty simple. There is no real way of measuring the workload of a body(yes we can throw on SRMs and guess the body is about 25% efficient and work out the total amount of calories spent through an SRM is multiplied by 4 to give what out bodies used in energy to produce those watts, but that's still guessing, they do say its very accurate). But after speaking with a mechanical engineer they set up my bike to be efficient. Then I went and spoke with then tested with Bio mechanic and asked them how do I become as efficient as possible to spin this position. I was able to get my position based on that. I dont want to say to much but some food for thought:

Your muscles are at most powerful as operate with greatest active tension when they are close to ideal length (normally their resting length). So to get the maximum out of the quad its best to be at maximum effort from 2:30 oclock to 6 oclock or while standing even 1 oclock and imagine the leverage on a longer crank while standing .

Cycling races are long... super long. I could hit the gym and hit hard weights or I can hit slightly less hard weights and be there longer....

I have my cleats further back, seat forward and all this combines with my position and also my longer cranks, Then you look at femur to crank length ratio that just destroys everyone theories all together....

Im not saying longer is better, I personally tried 172.5, 175, 177.5, 180 and 185mm. I ride with what I feel best. You should ride what feels best for you

[LeDuke]

So, Zakeen, can you pull yourself away from your long hours of being a Protour hardman and take a minute or two to fill us in? And if you have any extra time, how about a step-by-step how-to to help guide us would-be DIY carbon shoe builders?

I dont like to say to much, so you are right in that way

But to say a few things I disagree of, which does not mean I am correct, I watched your video Cyclespeed and your points on why its better to have shorter cranks were:

Leg doesn't come up so high so you can get your torso lower just by having shorter cranks.

This has nothing to do with crank length, I run super long. Then I ride a frame a little smaller then I should, but I must do that so I can have a shorter steering tube, meaning my stem, without spacing is as low as possible and then I still have a negative angled stem. If I ran the a bigger frame then I wouldnt be able to get my handle bars so low(bigger frame bigger steering tube). So having said all this. I really have an extreme low bars and still my legs dont hit my torso. I did however move my saddle more forwards which opens up my hip flexors and tilled down my saddle which helped even more.

Cornering, you have less ground clearance.

Im able to race without this problem.

To get maximum power is hard and fast peddling and its easier to maintain that on shorter cranks because you said it is a lot easier to maintain that circle of high speed circle. If you don't have to do a great big circle with longer cranks which is putting a lot more strain on your joints

This gets more interesting. Power output is Watts equals RPM X Torque. So having a longer crank arm requires less Torque/strain( which I believe is better for your joints ). Doing smaller circles to maintain higher speed I disagree a little. Legs are going up and down, like pistons in a engine. Every time they go up, stop and down they lose energy and the muscle has to re-fire again. I feel its easier to maintain a larger circle.

You mentioned that if a shorter crank does a 12 to 6 oclock rotation then the wheel travels the same as a longer crank doing the same. Then you say that people with longer cranks are using less force(which is the whole idea), saving energy and must be good.... on that rotation. Then you say: But no its just a simple question of gearing, because all you have to do for the shorter crank feel easier again is just change up a gear. The shorter crank becomes easier and you are back to the same thing and you have no advantage of having a longer crank.

This is where I think you are wrong. If you are at the same place by simply changing up the gear, then yes you are right, the amount of force would be the same for the smaller crank to do that 12 to 6oclock rotation in a smaller gear compare to the longer crank in a bigger gear. Force might be the same(depending on gearing differences). However, the wheel rotates far longer in a bigger gear then in a smaller gear. So you yourself say right there, that there is a difference. Same force, different crank length, different gearing's. But one gearing has a longer rollout would mean that difference in rollout is the advantage of longer cranks. You would rider further with the same force applied on the crank.

Now I know its not as simple as that, but yourself there says it.

How I got to my crank length were pretty simple. There is no real way of measuring the workload of a body(yes we can throw on SRMs and guess the body is about 25% efficient and work out the total amount of calories spent through an SRM is multiplied by 4 to give what out bodies used in energy to produce those watts, but that's still guessing, they do say its very accurate). But after speaking with a mechanical engineer they set up my bike to be efficient. Then I went and spoke with then tested with Bio mechanic and asked them how do I become as efficient as possible to spin this position. I was able to get my position based on that. I dont want to say to much but some food for thought:

Your muscles are at most powerful as operate with greatest active tension when they are close to ideal length (normally their resting length). So to get the maximum out of the quad its best to be at maximum effort from 2:30 oclock to 6 oclock or while standing even 1 oclock and imagine the leverage on a longer crank while standing .

Cycling races are long... super long. I could hit the gym and hit hard weights or I can hit slightly less hard weights and be there longer....

I have my cleats further back, seat forward and all this combines with my position and also my longer cranks, Then you look at femur to crank length ratio that just destroys everyone theories all together....

Im not saying longer is better, I personally tried 172.5, 175, 177.5, 180 and 185mm. I ride with what I feel best. You should ride what feels best for you

That's a WorldTour pro dropping knowledge.

Thanks for stopping by, Adam, and good luck this season!

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