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Is Crank Length Important To Professional Cyclists?

Is Crank Length Important To Professional Cyclists?


It’s a commonly held belief
that the taller the rider the longer their crank should be. For example, a rider of around
six foot should have cranks of 175 millimeters, and a shorter
rider under five foot nine should ride cranks of
around 170 millimeters. But does this belief hold
any water in the modern Pro Peloton. Well we’re here at the
Abu Dhabi Tour to conduct an in depth survey amongst
the World Tour teams to find the answer to that very question. This is by no means an exact science, but a very rough formula
for crank based on height is as follows. This formula assumes that the crank length is around 9.7% of our
height and that everyone is of roughly the same proportion which, of course, we aren’t. It doesn’t take into account the length of the tibia, femur, and foot which of course are key
biomechanical factors. Now another important thing to point out is that cranks are only readily available in 170, 170.5, and 175 millimetre lengths. Riders under 175 centimetres in height only have a 170 millimetre
cranks and above as their option. I race on 172.5, then laterally
175 millimeter cranks, but the formula suggests the I should be on the 177.5 cranks as
I’m 183 centimeters tall. That all said. What does our sample of
100 World Tour riders indicate to us. It’s this rough formula
a useful guide or not? Dimension Data pit now. That’s Igor Anton’s bike. He’s a climber pretty small. I reckon he should be on 170s. Let’s check. Yep 170s fits with the formula. 30 of the sample group
used 170 millimeter cranks, and their heights ranged
between 169 centimeters and 181 centimeters. 43 of the group were on
172.5 millimeter cranks with heights between 172
centimeters and 187 centimeters. 26 of the group rode 175 millimeter cranks with a height range
between 182 centimeters and 190 centimeters. From this, we can see
that riders largely stick within the formula. Does this mean that the formula is right? Well, no. As you can see by the height ranges, there are more than a few
anomalies, and one rider, our friend Adam Hanson was out on his own riding 180 millimeter cranks
and he’s 186 centimeters tall. Adam, we know you run pretty
long cranks, 180 mils. How did you come to that decision
to ride cranks so long? – It first started years
ago. When you had an SRM Used to have to work
out the slope yourself in those big formula for you. Five kilo weight and it
was all pretty complicated. You had to put a crank length in there that sort of surprised me. I worked out from that that power equals torque
multiplied by RPM. My theory was always based on
okay, so the longer the crank the less torque you must put on the pedal. The less weight you put on
the pedal for the same amount of power. For me it’s a more
efficient way of riding. A good example is if you
take a nut off a wheel of a car, if you have a short
leverage it’s really hard. But with your long one it’s
easy to change the tyre and take the nut off the wheel. It’s a lot less effort that
has to be put in for the same amount of force. I spoke to a few mechanical engineers. I prefer to speak to them
to a biomechanical engineer because a biomechanical engineer
knows more about the body, but doesn’t know the effect
of what the body does onto the bike. The best for your body to
produce at maximum power, but that power transforming from the pedal back to the back wheel,
that’s more mechanical because it goes through crank arms, right? A mechanical engineer will
say it’s far more efficient to have a longer crank. – That effects your, it’s simple physics. Isn’t it? It’s leverage it’s far more efficient, but you’re a pretty tall guy as well. So I guess you’re more
predisposed to be able to ride efficiently with
longer crank as well. – Well if you talk about rider height, Pantani’s 180 cranks. He’s short. He’s super short. He used to climb like a goat. If you compare the crank
lengths to ratio of the leg, I’m actually using super short ratios like my crank arm lengths and my leg ratio to Quintana. I’m probably 40% longer legs than him, but my cranks not 40% longer than his. Maybe like five or 4% longer than his. I truly believe it comes
down to manufacturers. Shimano, Campag, and Sram I don’t want to say bad things about them, but I know bike shops they cannot have 20 pairs of cranks. They want to make a standard 172.5. Everyone rides 172.5 here. Okay, if you’re huge
you go to 175 or 180s. So it’s just easier for
the bike manufacturer to make one standard crank
length everyone rides and that’s it. – A short answer is a lot of thought has gone into determining your crank length without
a shadow of a doubt. Absolutely fascinating! – For sure, I wouldn’t
just jump on anything. – One of those anomalies from
our group was Nairo Quintana. He was the shortest at
167 centimeters tall, but rode 172.5 millimeter cranks. At the other end of the
scale, track rider John Dibben at 185 centimeters tall rides
only 170 millimeter cranks. We’re here with Katusha. They’ve got one particularly
tall rider, Ilnur Zakarin who according to the formula should be on 175 millimeter cranks. Let’s go and check. So here’s Zakarin’s
Ultimate CF SLX, red cranks. Let’s have a little peak. Ah, 172.5 interesting. This is Julian Bernard’s
bike, and as you can see it’s a very, very small frame, so you’d typically think this rider being a small, light climber
would 170 millimeter cranks. Let’s have a look. And he actually bucked the
trend a little bit 172.5. The formula is a rough
guide and only that. There are number of other
factors we haven’t touched particularly cadence and riding style, and that’s another video entirely. We know this topic will
ignite the comment section, and we’d love to hear
what you have to say. Well, I think you’ll agree some very interesting results there. Now so you don’t miss another GCN video, how about subscribing. Click on the globe. It’s absolutely free. Now sticking on the subject of cranks, how about clicking just up
here for a GCN science video when we look at importance
or not of crank length, and click just down here
for the importance or not of saddle height.

100 comments on “Is Crank Length Important To Professional Cyclists?

  1. I have heard Adam interviewed a few times now, he gives a really good explanation for everything and puts a lot of thought into his answers, top bloke!

  2. Longer cranks only provide more leverage if you're riding a single speed, if you have gears then the only argument can be from a biomechanical standpoint

  3. The longer the crank the farther the feet need to move. The higher the leg will be when it pushes down. visualize yourself on a leg press machine. The more bunched up you are the less weight that will be lifted. The amount of weight that can be moved goes up when the seat is moved back. Try that some time.  Shorter cranks are better.

  4. I always thought crank lengths referred to how long the other half would complain when I said I was going out on my bike. #informed

  5. Hansen is a clown. Your body isn't a motor. You can't develop even force around the whole crank revolution. Every body is different. Experiment and find out what feels right and what produces the most power and also what length causes least injuries. It's not as simple as asking a mechanical engineer. That is a simplistic approach

  6. I'm 5'7" (30" inseam, but not sure about my bone lengths) and have ridden 170mm cranks for years. A few bikes ago, I tried out 172.5mm cranks…..I felt like I was a little more powerful on some climbs, but overall, my hip angle closed a bit due to the lower seat height and my cadence on the flats dropped significantly. I went back to 170mm cranks and was much more comfortable.

  7. I have not read all the comments, so I don't know if anyone has mentioned this already, but anyway.
    Along the travel from the position where the cranks is "pointing up" to where it is "pointing down", your knee produces more power where it is more extended. Therefore, the shorter the crank, the less your knee will bend (because the highest and lowest points are closer), and the longer it will be within optimal "power/angle ratio".

    Does this make sense? It does in my head.

    Of course, a longer crank produces more leverage, but that is the mechanical side.
    The bio-mechanics of the knee, on the other hand…

  8. And really, what is the difference beetween the produced cranks? 5 millimeters which is barely 3 %. Ridiculous to think that has some effect on movement. So I think the manufacturers are bastards and think only about money.

  9. Saying a longer crank makes you more powerful is like saying lower gears make you more powerful. They don't. If you have a way longer crank you just ride in a longer gear to make up for it. Sum=0

  10. I just wish longer cranks were available in prices that didn't make my wallet fold up and run away screaming.
    The Formula says I need ~198mm cranks based on a 92cm inseam.

  11. If you think a few mm is going to have an impact on your pedalling and power out put then you've fallen for marketing. The longer the crank the better the mechanical advantage.

  12. Would it more efficient/effective to have smaller frame and wheel and at same time have bigger front gear and longer crank?
    in another word, having lighter bike with the same power transmission or same power/twork/rpm.

  13. Would it more efficient/effective to have smaller frame and wheel and at same time have bigger front gear and longer crank?
    in another word, having lighter bike with the same power transmission or same power/twork/rpm.

  14. It would be very interesting to see the correspondence of riders cleat position to crank lenght. Specially in the ones where the measure don't fit the usual formula. In a matter of pure physics a setback on cleats of 5mm compensate largely a crank 5mm shorter or even more. There is an interesting solution to compensate problems like this one, specially in short cranks:
    http://www.ebay.com/itm/New-drill-position-in-cycling-shoes-Cleat-set-back-Near-middle-foot-cleat-/152455458004?hash=item237f0dacd4:g:VScAAOSw3v5YtsEc
    What a difference with a setback of 12mm that original cleats fixation didn't allow. Like change from day to night! After the period of adaptation, to me took 3 weeks, it's like ride a bike in turbo mode. Now I use higher gear ratios without calf muscle pain and a much better performance. It isn't cheap – postage costs are high due to country or origin, but worth every penny!

  15. All about the Femur length. Height is irrelevant. Formulas are "rough guides" . Its a circle people! Longer crank, bigger circle, period! Not always better. Leverage smeverage. Spin faster to go faster.

  16. Rider height aside, it also depends on where your muscles connect to the bones. Some riders may have power advantages at certain positions. I'm quite sure all these teams put these riders through stress tests to find this out.

  17. Always a great watch when I'm watching GCN videos; but I found the information here to be especially useful for me today in my fixed gear endeavors. Cheers!

  18. That video should have been called, what is the effect of Matt's different hair length? Loving your work though Matt!

  19. I am inclined to think foot size should be a factor not just height. I am 186 cm and use size 44 shoes. 175 mm cranks just don't work for me. I use 170 mm cranks. It is strange how such a small difference is so noticeable.

    The argument that longer cranks let you apply more torque doesn't really stack up because gears are what determines how much torque is applied to the rear wheel.

  20. I'd like to see the next vid then. Interested by interview with Adam. I am 183cm and just ride standard 172.5 that came with bike. That said how much difference does it really make and is it worth the money. Although I generally find when replacing chain rings it's as cheap to buy a whole new chainset

  21. In American style of racing with "crits", it would seem the shorter the better, as there are continual jumping and surging where leg cadence is at a premium!!!

  22. Marc Madiot (1.76m) had no trouble bashing 180mm cranks when he raced and as Adam mentioned Pantani ( 1.72m) used 180's, as did Indurain ( 1.88m) .. compare that with Cipolini (1.89m) and his 172.5mm and Chris Boardman (1.75m) on 170mm… So, still no rhyme or reason half the time …..

  23. Hmmm. An interesting video. I'm 6ft and tend to train mostly for indoor velodromes where I use 165mm as there is a regulation limit due to angle of banking but for my road work I use 170mm. My 'most comfortable cadence is 100-105 for longer efforts but goes up to 125-130rpm for pursuits and maybe 145rpm for sprints. From the perspective in this video I am loosing out on power in some circumstances. I can't change crank length for velodrome work obviously, but what is everyones view about going to a longer crank say 175mm for outdoor training/base work/recovery rides. Would specific metabolic/muscular/biomechanical adaption be lost switching between 165-175 cranks during each training type ?

  24. Do you think They really ride on let's say 172.5 mm or are the cranks custom made to, for example, 172 mm or 173 mm. ? And if so, is there a way to get cranks in the exact size you want?

  25. I'm no expert and you'll probably see that easily, but you, (and the industry) seems to focus on crank length according to 'matched' height. I'm sure height has next to nothing to do with it, but leg length does. The crutch to pedal (seat surface to pedal surface) distance is more appropriate. Just because one person is 181 cms tall and the next person is also is 181 doesn't mean they have the same leverage when person 'A' has and 86cm inside leg compared to person 'B's 80cm inside leg. Who is likely to have the better push-to-power output ability? Any body height from saddle up is surely not contributing to the drive-power output ( short of breathing, energy supply and forward vision.) and has no need to be linked in an overall maths package to a long/short crank arm.

  26. 165mm cranks are readily available. I'm a huge 5'6 and have a 105 on winter bike, sram red on summer bike. Both in 165 length, and both were in stock online when I ordered. Good point about leverage… I've tried a 160mm length crank and although I liked the fit of the crank, I found it too difficult on steeper sections, 12% plus, of climbs. That loss of leverage is really noticeable out of the saddle, although, I guess more gears could fix that. Also, yes, it did affect style of riding. The shorter crank required an easier gear selection on the rear and increased cadence to maintain what I could do with the 165mm crank.

  27. On a road bike I like 175, especially for climbing out of the saddle just for leverage alone. But on a flat ride I like the shortest possible, my thought being the shorter the radius of the crank the shorter the circumference of the circle the pedal is in. More rpm equals more speed. That's my thought on it anyway

  28. any mechanical engineer, or anyone who has even taken a high school physics course, can tell you that the difference between 170mm and 172.5mm is negligible and the ONLY reason a company would develop both sizes are to make money. there will be NO noticeable difference in applied torque or comfort. This is coming from a mechanical engineer (me) but it doesn't take one to understand this basic concept.

  29. I just purchased a pair of 175 cm cranks I am 5.9 and my inseam is 83.82 or 33 inches. I am using this for mountain bike and I am more of a masher than a spinner. Should this be ok?

  30. I run 170mm and 172.5mm on different road bikes.  I honestly cannot tell the difference outside of adjusting saddle height.  On the mountain bikes, I ride 175mm cranks.  Maybe the longer cranks make a difference with my actual cadence, but I don't see a huge difference in power output.

  31. Its all in your head. How many races have you lost by less than 1 sec.
    Adam Hanson is wrong. Longer crank does not mean more efficiency.
    You need to look at what you loose not just what you gain.
    Pantani – EPO, Cocaine and anti depressants. So Adam should we do this as well.

  32. Calculator say i should have 182,5mm cranks. I have oviesly pedal many years at 175mm. Now i tested 180mm and they feel totaly difrent. Cadence was 88-100/rpm on 175mm and tested 180mm it is 75-85/rpm. That feels loW. But watts are easyer to get upvard on high intervals but on long ride i don't get what i use to have on forvard enthusia. Maybe time will prowide that.
    And it totaly sift my riding position that are more front than 5mm it just must be.
    So i learned to high cadence on 175mm and hope to have more endurance and distance cains with long arms. Make long rides with tall rider-video to show this. I can't , sorry.
    Ps. Somehow i can pedal from toptube position with shorter cranks easyer now???
    #mysticalcycling

  33. Matt explained so well, manufacturers dont wanna spend too mutch money into sizing their parts to your needs, they just wanna make money ! though I think its more important what gearing/pedals you have/use 🙂

  34. So if I have no issues having my knee touching my chest, what stops me from winning races with 190mm cranks? (provided I have enough ground clearence and that I can find such sizes somewhere)

  35. I have a 56cm trek madone with 300mm cranks. they drag on the ground and gouge the cement when I pedal but damn they're torquey.

  36. i'm 6'0 and use 175mm cranks on my road bike and thats here in the mountains in NC. I'll do several centuries and 100k's a year.

    but I much prefer smaller 172 or 170mm on my mountain bikes. when i have the larger cranks on the mountain bike with the lower gearing I don't feel I get the pull I need with larger cranks especially going up climbs. Some mountain bikers claim smaller cranks clear obstacles easier, but Ive never had a problem clearing with 175mm cranks

  37. I have always wanted to give some really long cranks a try. By that formula, I should be riding 188mm cranks, and I have very long legs, even for my height, so that would suggest even longer.

    The problem is that even 180mm are usually only available in expensive versions (no 105 or Tiagra), so I have no practical way to even find out if it's better for me.

  38. Shimano used to make their cranks in more sizes. Back in the 8 speed days, Dura Ace cranks could be purchased in the range 165mm, 167.5, 170, 172.5, 175, and 177.5mm. Ultegra cranks ranged from 165mm to 175mm, in 5mm increments.

  39. Does the UCI allow crank lengths to be changed from day to day in multi-stage races? Seems it would be handy to go longer when there are big climbs in the day, when the increased torque available becomes more important, particularly with less time spent in the saddle. Easier to make a break from the front too. On flatter stages cosseted in the peloton, the greater torque may not compensate for the extra leg movement.
    Are Pantani and Quintana the only great climbers with crank lengths greater than 'expected'?

  40. I'm 186cm and ride Rotor3D+ 150mm cranks on my trip set-up. My FTP went up, so did my cadence and my aero position is more aggressive. Loving it.

  41. From an engineer who models RF.: the answer is simple: we must use basic mathematics and engineering to solve this question. Logic alone does not cut it. It simply boils down to how much power the rider applies AT THE CRANK. Stating the issue this way makes gearing irrelevant (assuming one always uses the right gear to achieve the optimal RPM). There has to be a variable curve of max steady power vs crank length for the average rider. Measure this bio mechanical constant (i.e. average for all riders or for any one rider) and you get your answer. Power is RPM X torque. It only makes sense a longer legged rider can spin bigger circles at the same force and RPM (same force providing higher torque) vs a shorter one. However like everything mathematical, there would be a point of diminishing returns. Hence the peak of the curve must be measured, and this is simply where you want the length to be.

  42. You don't apply torque to the pedals. You apply force to the pedals, and that force multiplied by the crank length is the torque produced at the axle (T=F×r). So the longer the crank length, the more torque produced, however, your rpm would drop due to the greater circumference (2πr).

  43. It's not height per se, but leg length, and how that length is divided between upper and lower leg. There's no way 6'4" Michael Phelps (swimmer with long torso and short legs) should have the same crank as Christian Knees (Team Sky) who is also 6'4" but has much longer legs.

  44. Pro bike mechanic for 20+yrs.
    It's worth thinking about everything in this video plus the latter mentioned riders cadence/pusher of a gear or spinner etc & riders style to determine the individuals correct crank length. From there a formula can be used, it's also worth noting the pro riders comments as a lot of scientific sence is talked about & very relavent on this subject.
    Basically don't assume your crank length but see someone with the correct knowledge who will asses you to determine.
    A good % of my bike fit customers do ride the incorrect length as this is evident on feedback received from them to my questions plus body measurements, type of riding etc.

  45. I understand the point is that not all riders choose to go with the "formula" length and there are other factors. But, shouldn't the formula be based on inseam length and not height? My legs are relatively short for someone my height, my torso is relatively long for someone my height. Of course I'm a fat old man slow rider so it doesn't matter for me. But, I'm just saying that not everyone the same height has the same leg length.

  46. Hi, I don't race because of my age, but for me I use 170mm cranks and I'm 5'11". I have a weird body where my upper torso is long and my legs are short. So I'm right at the edge of the crank length formula.

  47. I'm 5'4" and ride with 175mm cranks… so there is no really no right way to ride a particular cranks. Leverage is king !!

  48. So the moral of the story is that the human neuromuscular system is really good at adapting to its environment. Unless you sit on the extreme ends of the body size spectrum, JRTFB…. just ride the f-ing bike.

  49. It's just all about preference plus everyone's body is different, a shorter crank will also change your seatpost height higher and a long crank arms one will set it lower… so all that all can change your bike fit a lot… It's all about what works for you to be honest… But he's right.. It's all about manufacturer, you should be able to change your size from multiple but it isn't the case for the most part.

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  51. 6'1" and I use 153 mm crank arms . Good spin , lots of power, and far nicer to my knees. I use to run 172.5 but age caught up to me.

  52. 4:08 No a mechanical Engineer (who has at least a bachelors degree and doesn't just names himself an engineer) would never say that, not even if he was totaly drunk.

  53. It's always a trade-off because if you go to a shorter crank your knees won't need to work as much but it will need to work harder. The longer crank will give you more knee flex and leverage. I have a 30 inch inseam and I find 172.5's comfey.

  54. Check out Zen Cycles in Colorado – they’ve been making custom length crank sets for years. And you cannot base the crank length on the riders overall height?! Must be based on inseam length – I had a cycling accident that resulted in a bad left knee that can only bend slightly past 90 degrees – so I had to go to a much shorter crank just to allow my knee to pass through the top of the pedal stroke.

  55. I personally believe that crank length is due to the size of the frame …

    Now this is my own thought on the matter I don't think I'm right and anyone is wrong It's just how I find it to work for me.

    So my riding style is I like my saddle about give or take a few mm

    2.5 mm above the hight of my handlebars and its a give or take

    Could be 2.8 or 2.2

    But that's where I feel comfy with a nice bend in the elbow when I'm holding hoods

    So I just ride a size crank that let's me get around a 30 deg bend of the leg

    And touch wood I ride pain free

  56. I don't think it has as much to do with rider height as it does wether you prefer more torque or more efficient cadence. Longer = more torque at the expense of slower cadence, shorter = more efficient (faster) cadence at the expense of less torque. I'm 5'11 with short legs and I'm more of a grinder spinning at around 70 rpms so I prefer 177.5s because it's the longest length where I can still maintain an efficient cadence.

  57. Surprised that no one has figured this out yet. This is mainly what sets team Sky apart from the rest. They run specific crank lengths based on the course or strategy. The crank length you choose can significantly impact your power output and most importantly in the TDF, recovery time.

  58. I’m 6’ 2” my first true road bike came with 170mm cranks, I switched to 180’s around 1990 and they felt amazing & my 2 current bikes have 180 & 177.5 respectively, to be honest I can’t detect much difference between these two lengths but I tried a demo bike recently with 170’s and the circle felt really small and I didn’t like it at all. I always have to special order the long lengths when I get a new bike though, but it’s worth it to me.

  59. I think what Adam is talking about, when he mentions leverage, is putting less stress on your muscles. Have you tried to undo a wheel lug bolt with a small tool versus a large tool with a long handle? Doing that over and over again with the smaller tool is gonna tire you out more quickly.

    Also, almost everybody in the pro peloton has the same gear ratios. 53/39, 11-28

  60. if you want a low/slammed/Aero position, don't go with long cranks 180/177.5/ or 175s. that extra 2.5mm could be your knees bumping into your stomach

  61. Ever since my XL Surly Moonlander came with 180mm Surly crank arms, I’m totally hooked on longer. I’m only 6ft, barefoot, but am all leg. I’m currently looking to replace my 175mm on my gravel bike with a 9 speed triple 180mm. I might even go with a 185mm, but that’s a couple hundred more dollars. I find I have no problem with spinning at high rpm either.

  62. cranks all depend on height, purpose of riding (climbing, speed, etc), leg length, position on the bike, whether you stand or sit more often, sprint, etc.
    I'm all about top speed sprinting. so I don't sit too often, which the crank doesn't affect knees. I'm 6'1". a bigger crank provides better leverage, slower acceleration but higher top speed.
    most people think you're disadvantaged with a bigger chainring/crank. on a straight track, you may accelerate 10 seconds faster, but within 1 minute I could zoom by you at a top speed. once I reach a higher speed, the effort is reduced dramatically. I could be pedaling with minimal effort to hit 40 kph, while you'd be pumping at 130 cad. the disadvantage is a track where you're constantly stopping.
    so everything is relative to everything.
    the taller:bigger a person is, the more predisposed they are to greater power. an average healthy 7-8 ft tall man, could be as strong as a pro weightlifter at 5'5".

  63. I'm 170cm and ride 175mm. I haven't had any trouble, but it's my first bike so I wouldn't know what trouble is.

  64. Pantani used 180 because they had a simpler belief that the longer the lever the more force was applied. This was an incomplete solution, Power=Torque x Cadence. Biomechanics takes into account the human biometrics related to the bicycle's mechanicals. Adam, please stick to designing those great looking shoes.

  65. Hansen is wrong but he is on the right track. You do not gain power by making the cranks longer, because power can not be created or lost. So if more power goes to the back wheel, it means you are putting more power in. In this case, taking longer cranks will raise your leg speed which will in turn demand power from your body. But he has a point in saying these standard crank lengths and formula's are BS. The cranck length largely depends on your pedalling style. Not everybody's muscles are the same, and we all use them slightly differently. For some riders the increased leg speed reduces their efficiency, but for others the extra leverage increases their efficiency. So biomechanics are extremely important here! I think the length of your powerstroke, and wether you like high cadences or not, will largely decide wether long cranks feel better or not.

  66. I developed an oscillating pedal that is very efficient and it is the World's Simplest design. Use a conventional bike, just remove it's cranks, spindle and chainwheel then assemble this invented mechanism . The conventional bike frame's bottom bracket will be the housing of this invention….. https://www.youtube.com/watch?v=n1ZPA…

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