If you need to know your personalized crank size we recommend this app: biometricbikefit.com/. also pls help us by filling this google form about your current bike fit: bit.ly/bikefitdata

wow, that music is something else! Silence is golden my friend.

I changed from 170mm to 165mm and agjusted fit according and my hot knees and sore lower back disappeared. When i built my bike i asked for 165 but shop said no you need 170 woodnt go any smaller than that after 2 yrs i bought a cheap sora 165 crankset and put it on as a trail and just raised seat by 2.5 mm and even by doing that i felt better. Im 5ft 6" Power, position and comfort all greatly improved. Great video as always

I'm always appreciative a good coaching and bike fitting content. For many reasons, crank length has been of particular interest to me for decades. A couple of initial points I'd like to make: 1) Thank you for your asymmetrical crank length "experiment" near the end of the video. I have witnessed in others as well as experienced myself the same very surprising lack of sensitively to asymmetrical crank lengths. 2) Thank you for doing of good job of highlighting and explaining the differences in fit geometry associated with cranks, including the opposite differences in body/leg angle from the top to the bottom of the stroke. Now, for the real motivating factor for this comment: Both your initial introduction and final conclusion (both being the same thing) are fundamentally flawed and unsupported in your presentation. Your presentation does a fantastic job of explaining all the reasons for different crank lengths, independent of body dimensions from foot speed to flexibility to riding style and purpose (much of which can change over time, even within a season). You even get to the point of demonstrating that, after of few minutes of riding, your body readily forgets about a 5 mm change in crank length from one side to the other. Then you go right ahead, essentially ignoring everything you've just presented, and conclude quite strongly that there should be a specific and correct crank length for each person. And you seem to base this entirely on your personal sense or need for symmetry or what you perceive "should be" instead of what is shown to be (frankly, in line with Leonard Zinn). However, in line with your observations, studies have shown that over a surprisingly large range of crank lengths, once a rider has time to train on and acclimate to different crank lengths there is not a measurable difference in performance from one length to the next. Finally, as a coach and bike fitter, one should be quite aware that just because a cyclist feels like their fit (including crank length) is right or wrong does not mean what feels best will provide either the best performance or the lowest risk of injury. Heck, it is reasonable to have different crank lengths on one's time-trial bike than ones track bike or ones road or mountain bike As Andy Pruitt has frequently suggested over the years, a good fit is a compromise between a somewhat adjustable machine and a somewhat adaptable body. In the end, I argue that factors other than body size are critically more important when considering crank arm length.

I'm 178cm in height and ride a 54cm (medium) frame. I changed from 172.5 to 165 on two bikes and immediately felt more comfortable and now my average cadence is higher too. Love it.

Went from 172.5 on my Tri bike to 165mm and if I change again it will be to a 155 or 150. For Ironman racing as far as I can see there's no downside and the upside is less tightness in the hip flexors when you get off the bike a try to run a marathon.

The ‘music’ in the background is really disturbing your theory and makes it more difficult to comprehend. Actually I cannot see the whole vid because of the noise.

Very helpful, thanks. I will change to longer cranks!

You nailed this one, great job!

I always find your videos useful. Thanks for sharing that app. I am checking it out now.

Thanks for doing a video on this topic

Immediately subscribed!

Great cacth up on you previous blog about crank size. Specially like the experiment "riding with two cranks of diffrent length". Think the adaption you speak about is comparable with riding cranks of the same length but using Rotor OCP (Oval) chain rings. In that case pedal velocity doesn't differ by leg but by angle on the pedal circle. (You get used to it after 30 Minutes) Combining longer cranks with OCP rings is what brings real power. When at the 90/270 position of the pedal stroke your pedal speed slows down and you have "more" time push at your max momentum. Looking for ward to see more info on that in a furter blog

Wow that was extensive! Thanks!!!

I am 180cm and I use 172.5mm cranks on my road bikes and 175mm on my TT/MTN bikes. I've played around with swapping them around, but this setup feels best for me.

love the science and logic and presentation. keep more comming please

7:27 great point about the double whamy and what's also interested is that if you move your cleats lower to the toes that position brings your foot back and closer to the hips closing the hip angle even more and causing triple whammy

Would love to hear your input on how all this information applys to singlespeed or fixed gear and out of saddle pedaling

Great video on crank length for years I've preached on club rides about crank length! Your spot on that a lot cyclist are riding the wrong size crank and mostly to long a length! I blame the manufacturers on this, that was a great example on the chart you showed illustrating that! I have a 30.5" inseam and I have ridden 165mm for 5 yrs. I have been told for years that i'm on too short of a length crank by different shops! 4 yrs. ago I went on E-bay and bought 4 ultegra cranksets 165m I wanted certain club members try them out These members had inseams relatively close to mine! All 4 of those riders tried them and were amazed how much more comfortable they felt and they all converted over. I wish the industry would make more shorter cranks available like a 167.5 and a 162.5 the riders with shorter legs should have the shorter increments available, instead its the other way around the longer leg inseams get the short increments! From a ratio perspective it only makes sense that riders with smaller inseams should have closer increments! Again great job on the crank length, one of the best videos out there explaining crank length!

It would be very interesting to ride different crank lengths with dual power meter pedals and see if power changes from side to side in your pedal stroke. Great video thank You Rick D.

as a relative noob i sensed my 170mm's were too short for my 1.78m height and pedal-mashing style.. so i upped to 175's without much thought and wasn't expecting much from that 5mm increase but wow it is night and day for me, so much better. i got lucky hitting my ideal number

Rode 175mm cranks many years until 2015 and a new 56cm bike with 172.5. Had bottom bracket issues so I sold it and used my old 58cm with 175mm. Bigger circles? Yes. I could spin up to 170rpm easily and found 175mm cranks served me best. However, I decided to experiment and I purchased 170mm cranks. Could not hit the high rpm but thought it was just due to a lack of adaptability. Had them on a month and could hit 140rpm but was hard work. Got a new bike and put 165mm cranks on. Yes, tiny circles and an average cadence of 94 on 4 hour rides. Hip angle was open and knees didn't come up as high and may have offered an aerodynamic benefit. Pushing bigger gears didn't feel great and was counter-intuitive I suppose. Standing and climbing in a bigger gear felt ok. I discovered that any efficiency losses were out weighted by my perceived effort: 175mm just feel better. I do agree that the brain makes pretty short work of adaptation. I don't think I would generalize on crank length versus inseam as there are many other factors to consider. I appreciate your videos and the information that hey provide..

Never had any complaints.

Great video! It'd be nice if you had another person ride the bike with different crank lengths to see if they notice it. I personally doubt it. Human body is incredibly adaptable.

Great video

Excellente content. But please down play or change the background music as it is distracting. Thanks

Great video. I have bikes with 170,175,180 and 185mm. 170mm is too short, I riding with my ankles instead of legs. 180 and 185 are fine, don't feel much difference. It seems my preferred rpm is on all bikes the same. Bad thing nowadays, you can't buy longer cranks anymore (SRAM, Rotor etc don't make 180mm anymore)

outstanding

I am 6' 4", 175 felt too compact, 180 Shimano feels so right for me.

I have suffered with too longer cranks for years! The pain in the knee and the dead spot at the top of the pedal stroke has caused the loss of power!

5’10- 172.5mm on my Road Bike. 170mm on my Fixie. I just purchased a 165mm set of arms for my road bike today. My knees graze my elbows just a little bit when im on my tops down as low as I can get aero. My goal is to let this 165mm length to allow me to get lower and not graze my elbows. I believe the shorter crank will be my solution. I am very comfortable on the 170’s on my fixie and actually I hit my peak power pr on my fixie over 1700watts this past summer.

One thing no-one mentions - is that, ceteris paribus, a longer crankset facilitates greater fat burn, owing to the broader range of motion of the legs.

Talk about foot/ankle angles and movement with a change in crank length and what about midfoot or farther back cleat position and who that effects pedal stroke with shorter cranks.

I find with my knee height at the top of the stroke, there's an amount of knee drop where I have the most power and comfort. Then, if I'm stretching at the bottom of the stroke , I need a shorter crank arm.

Nice video and presentation. I think that optimal crank radius should be a ratio, percentage, of our inseam. And more specifically, to the femur, bone length in our thigh. On the other hand, ergonomic lab data can lead us to an optimal task specific swing angle, between torso and thigh. The optimal crank angle will be derived from (1) femur length, (2) optimal swing angle and (3) factor in our Tibia and ankle height. We’d be surprise of the result in that compare to what we already know or what we think we knew.

163cm height. 71cm inseam. 155mm cranks. Average Cadence 95-100rpm and max RPM I've achieved is 210rpm on the trainer. I've found that dropping the the crank rings down by 2-4 teeth helps with the leverage/cadence issue. Rotor is your friend here!

I never had a bike fit but it was pretty obvious to me right away that 172.5 wasn't gonna work within a few months of riding my first road bike. swapped with 165 and couldn't be happier. My issue was that my knees were hitting my chest and making me bounce in and out the saddle (has nothing to do with saddle height. saddle height is set with cranks in lowest position. with that setup my knees would hit my chest when cranks were on the top position). It was outright dangerous going down hill cause I couldn't easily get my knee out in the direction of turns or quick shicane type turns it was hard to change direction fast. Everything is smooth now and I have a rock solid upper body and all my joints are relaxed with 165.

It was about 20 years ago, i was putting together a bicycle from scrap parts. Lacking proper tools, I could not remove one crank arm, so I used two sides from two different sets. Then, when riding in a rolling hills area, I noticed I often get short of gears and have difficulty to complete the revolution with one side, never with the other. Until that point I was totally oblivious to a fact that different crank sizes exist. Imagine my surprise when I finally discovered that these two arms were of different length. The one that was so difficult to complete for me was 170 mm, the "stronger" one was 175 mm. So I thought, if the longer one (of these two) feels so much better, what if I get a crank even longer? When I found a used Race Face crankset 180 mm I went for it without hesitation. Now, I am 191 cm tall, inseam 91 cm, shoe size 14 or 48. This 180 mm crank suits me very well in some situations, especially on a gravel and in a mixed terrain where one just can not spin out. On a road, though, on a pavement, I think 175 mm is better for me. However 170 mm always feels wrong. So, for riders with smaller numbers than mine, I would advise to be very careful with increasing the crank length -- one could loose the speed and power explosiveness.

I guess feel is a factor as both Marco Pantani and Big Mig rode 180 mm cranks. Maybe femur, tarsal & metatarsal have a significance, whereas toes don't?

You right no one talks about cranks size

Done 175 they're massive, 172.5 bit long and 170 feel ok...tho it'd be interesting to try 165’s...

This might explain my slow cadence. I'm riding a 175mm crank and I'm about 177 cm. Should also add I'm on a mtb.

Two different sitzes of cranks are a good idea if you got different leg length.

I went from a 175 to 170mm crank last year, thinking it would not be an issue, and suffered from lots of biomechanic issues. The fact that I spent quite a bit on the new crank (power meter) made me reluctant to just get another one in 175mm. The video didn't seem to mention the change in position of the knee relative to the pedal axle on the downstroke, something my physical therapist is trying to help me with after a year of on/off knee pain despite my efforts at making the corrections to fit doing everything listed in this video. Do not underestimate the body's muscle memory - the change in kinematics seems very small from a numbers perspective, but if you are in the saddle for several hours at a time several times per week, the the body can be resistant to this type change without very careful attention to how this change is managed. I am hopeful my knee and the joining hip muscle groups will be receptive of my physical therapy to make a full recovery, but it has not been an easy year.

If we ask a gas engine engineer he may reply that crank radius relates to the Tibia+ankle height (piston’s push rod)

I ride 170mm lh crank, 172.5 rh crank, because of a lh hip replacement, and longer crank causes impingement of hip. I can certainly notice the 2.5 mm difference, if I was to ride the longer crank on lh side.

Thanks! With my 180mm CS I’m well below fit size according to any formula (I have them on all my bikes). But it's become more difficult (expensive) since about 15 years, to get 180mm CS -- with Shimano having stopped making them, in all except Dura Ace models.

It honestly seems to me that, given the perfomance impact would be negligible for amateur riders (me), crank length really boils down mostly to bike fit.

40yr old 6"2 250lbs BMX for flat land distance. What crank length would you recommend?

My Gravel bike came with GRX 172,5 cranks from the manufacturer. At longer rides I feel very uncomfortable knee pain which I didn’t experience with my trekking bike with 170 cranks. Unfortunately, the smallest GRX 600 cranks available are 170s. Do you think going down by 2,5 mm from 172.5 to 170 will produce a noticeable difference for the costs? I am 178 cm tall with long legs and an 87 cm inseam. Or can you recommend any cranks other than from the Shimano GRX 600 series that are available with shorter cranks and would be compatible with a a GRX 810/600 2x11 set?

hi i am 5'9 with a inseam between 78 79 cm i am currently running 172.2 mm cranks that came with my bike i have toe overlap in my bike and am planing to change my cranks to resolve it and maybe to get more comfortable ..also running 50 34 planing on getting 52 36 cranks because in 34 plate i spinn to fast and has to cross chain will i notice any negative effect on this changes if u can help me please ?? or it will better just to get 165 mm cranks with 50 34

Thanks for the video - It's very difficult to find cranks under 165mm, had to get bikesmithdesign to custom cut one down for my 157mm, so much more comfortable! Too bad only alu cranks can be cut

How do I know? My knee hurts

UCI Hour Record timed by Tissot - Aguascalientes (MEX) / Victor Campenaerts: Cranks? Cadence? Pain? For sure..

mtb come with 175, 170 only. unless you are riding a kids' bike, you only have those 2 options - the big guys Sram and sister co's and Shimano created this problem, but others are here to fill in where the big guys and their R&D departments are failing. Hope, Cane Creek, and 5dev are all making shorter cranks. i opted for the 5dev trail cranks, with my 30mm inseam the crank arms at 155mm are what is suggested. for my GF, her inseam is 28" and i just put a set of Trailcraft (they make kid's bikes, nice bikes to boot) at 152mm you'll have to go down a couple teeth on the front chainring if running 1x going from 170mm crank/32T ring, i went to 155mm crank, 28T oval ring. my initial thoughts: my legs feel like they are spinning in a more natural circle, feels like i have more effiecient power pedaling, and it's much different than cranks that are too long where it felt like i was stomping out small fires when on the bike. do it! unless you are 6' tall, 170's are TOO LONG... and 175's prolly only fit giants. lastly, shorter cranks will likely require that you raise the seat height, OR if you mtb you can get longer dropper!

please try this with BMX bikes, changing the cranks and how it affects performance.

In my country, actually, Shimano's country, 170mm length for men's bike is defacto standard we see in bike shops. One day, I ordered a crank set upgrade (from 170 to 170mm) and the 2 days later asked to try changing it to 165mm. Shimano said a 165mm set is available but you cannot cancel the 170 mm set it's in processing so you'd have to buy two sets if you wanted 165... Eventually, I gave up 165mm trial. That's their business and bike industry do to a customer to make them obey their production schemes unless you are very willing to pay extra. Sad.

Shimano R7000 is a 2 piece crank with the smallest being 160mm. Ultegra and Dura-ace does not have this length. I am 165cm in height with an inseam of 73.6cm.

Good video. Very complicated to fine tune crank length so most people just ignore it instead. What I find is that if I raise my saddle to get a good knee angle at the top of my pedal stroke, then the saddle is to high because I cannot comfortably reach the bottom of the stroke. Also if I move my saddle back and lower it to correct the knee angle, then my reach becomes uncomfortable. Would you consider this a case for a shorter crank length or is my bike the wrong size which would mean that the shorter crank would make me feel comfortable but has not fixed my issue.

Good info but the music in the background is annoying. Keep up the good work.

Thank you very much for this information. Follow-up question for you: if you have an appreciable difference in leg length i.e more than a centimeter, would it make sense to run different size cranks - left and right - to accommodate the difference?

Can foot length, if not normally proportional to height or inseam, affect crank length selection? How? Thanks

Shorter is better for ultra distance. Much less pain in knees and hips for zero cost in speed. I am moving to 150 cranks from 165s to further optimize. If I was riding normal distances I probably would not think much about it.

When you start to ride fakie ( backwards) then you really notice what cranks are good for you , actually depending on the height of you BB.. not really for roadies but Im a street trials rider I ride 25T / front 9T back... and I cannot find any advice so I came here. I need high torque with a quick rotation. Saddle height is not an issue as Trials riders ride standing up....Do pedal kicks depend on the length of crank? any advice? thanks in advance to any non-roadies here by chance :)great video by the way I learnt a great deal. buit alas I have one gear and depend on my body not gearing.

i wonder if anyone have thought of making a variable length crank or a dynamic crank that would be cool

Yes, most people ride the crank length that came on the bikes they chose. Have you tried shopping for new cranks lately? In 2022, and if you are a new cyclist, and you buy a bike for $500-800, changing the crank length would cost 1/4 or 1/3 the price of your new bike. Who's going to do that?

I began cycling with 170 mm cranks and the more I rode the more I felt uncomfortable with them, my feet wanted to do a bigger circle than the cranks allowed to do. So I tried 180 mm cranks and from the first ride it felt much much better. Ride 180's on all my bikes since than (...and with every new bike it was a horror to get them...), still happy, never knee issues. Now the "new big thing" of bike fitters (at least here in Germany) is to tell every rider to go to shorter cranks - doesn't work for me; tried the 172.5 of my son, bad, unnatural feeling. PS: my inseam hight is 90.5 cm

I'm 171cm, inseam 81cm and all my bikes have 172.5 cranks. Most of these formulae suggest around 165 would be better, apart from the stevehoggbikefitting one that came out to 176! Surely that's a big outlier in terms of formula. Either way, would be good to test 165s... Shame it's not trivial.

Bottom line for me based on what I've learned so far about this topic? If you're young and strong, longer cranks. If you're old and decrepit, shorter cranks.

omg-the music is so stressful. Great video though

i expected more usable facts: some time i drove different sizes cranks and it sucks, on road bike is better to have shorter cranks (170) because is better to have more rpm at higher speed and shorter cranks better accelerates, on mtb on steep uphill is better to have longer cranks (172.5) because pedal rpm is low what gives longer lever for low rpm and high torque, if i drive it on flat i have disadvantage because it is hard to keep high rpm at high speed, then i pedal lower rpm until i have available gears

The lowly 167.5. A unicorn that pops up on eBay every now and again.

Nice video! I have normally ridden 172.5 but I just got a 175mm left crank arm power meter! I'm searching for a right side crank arm but dunno if it's ok to ride 2.5mm offset in the mean time?

I am 186cm tall and have driven 172.5 and 175 cranks so far. I've been riding 170mm cranks for a few days now. It feels a lot better even though I'm so tall.

pedal platform height figures in as well and pedal height can vary by millimeters

I ride an MTB, and am 6'2". So, I went with 175. Less downsides than roadies, and works great.

I was riding a mountain bike with 175.0 mm cranks and having sore knees afterward. My saddle height was correct. I needed to replace my cranks because of an interference problem with a new derailer. I decided to give shorter 170.0 mm cranks a try. Although the crank leverage was decreased, I was able to accelerate faster and ride faster WITHOUT any knee pain afterward!!!

crank size must be matched with leg size and seat position.

I bought a 120mm Syns crank for bmx, 38x17 on my fixie. I spin fast but it feels like actually the gearing is too tall. It's easy to spin 130rpm! But... I think I went a bit too far! hahahahah I think around 140mm would be OK for me versus the 170mm I've been using. I've tried 165mm already, feels beter than 170 but it wasn't short enough. I almost agree with that image that you should get the shortest possible, even if just to try it out. Remember to get small chainring(s) to go with it.

Part of me suspects that you made this whole video just for that one liner at the end :')

Im testing kids road bikes and i love them because they have shorter cranks and i pedal faster. Also no body questions the chainring size, i was in love with a bike with 44 teeth, bike got stolen

I honestly can say the market doesn't make Look-style cranks with adaptable crank length because they would sell so much less of them lol!! All cranks should be that way for the love of engineering and progress. More cyclists will have a better fit instantly.

any thoughts about track bikes? (not road fixie...track riding)

Will shorter crank radius make our bike a kid bike?

why don't bike fitters and riders consider femur head size and position and the acetabulum pocket depth and it's position on the pelvis that determines the crank length, all I'm hearing is the optimal lever lenght and aero gains which is rubbish if the cyclist can't sustain that extreme aero position with wrong size cranks. Think about how people have different squat positions, some squat very narrow and some with their knees pretty wide and they go wide because the femur head runs out of space in acetabulum and when you force the extra movement the femur moves deeper into flexion and puls the pelvis along causing pelvic anterior tilt. This postion can be duplicated on the bike also when the person is positioned in very prolonged and stretch out position on the drops with longer than optimal crank lenght that causes cramping sensation in the hips so the solution would be shorter cranks that shortens the femur flexion and the hip angle is more open

Should I use shorter crank length just to reduce toe overlapping in smaller frame?

I can´t find good short cranks :(

so what crank arm length should I choose?!

206cm height 4xl bike with 200mm cranks

👍👍👍👍👍

DO NOT rely on a global formula to find your ideal/optimal/preferred crank length. Road test/demo (ebay/LBS) before making an investment in new cranks & chainsets. To test your crank length you need to do a tough, slow cadence, stand-up effort, completing each revolution without a noticable dead-spot at the top of the stroke. Too long a crank and you will find your knees/hips flaring out in order to make it over the top; wasting energy and causing detrimental neuromuscular and skeletomuscular adapations (joint pain/damage. Moving from 172.5mm to 165mm was a gamechanger/kneesaver for me @5' 8" w/31" inseam). To optimise performance riders should use the longest crank they can fit (fit being the most important factor), with any difference in cadence being made up in ring/cog selections; longer cranks = shorter gears and vice versa. If you intend to remain seated at all times (e.g. for TTs) then you can fit a longer crank (knee/hip flare wont be a problem, but you still want to avoid dead-spots) and like before, make up for the cadence change with ring/cog selection as necessary. The long and short (excuse the pun) of it is this - if your cranks are too short, you may lose the ability to put a few watts on the road, but if they're too long you could do some fairly serious damage to your body. I've been there and it's not pleasant.

I ride 175mm cranks, due to an injury I spent the winter on a Wattbike which uses 170mm and noticed no real difference at all. I had a bike fit last month and now realise that if I wanted to go to 170mm I would have to raise my saddle and bring it forward which would require a change of seat post from a set back to inline, so I can see how these things are interconnected with each other!

I might go crankenstein my leg length is not symmetrical 🙄

160 mm crank: am I a joke to you??

I am riding 175 and see that according to the table should be riding a 170 I don’t feel any issue but I will try the shorter cranks next time for a different reason I get some toe overlap currently, especially if I fit mudguards. So an extra 5cm will fix that problem

I'm in my 70s and so I'm interested in preventing hip and knee pain and not torque or power. So, my question is more about how do I figure the crank length so I'll have the best hip and knee angles...

i can't even find short cranks?

What crank length is best for a 5’5” male?

But you can't actually spin faster on shorter cranks because... gearing. You'd need to actually change chainring to keep it equal.

Shoes and pedals can easily make a difference of 3 to 8 mm