Does Bike Crank Length Matter & Should You Change Yours?
ฝัง
- เผยแพร่เมื่อ 11 ก.ค. 2024
- Bike fit expert Jake Yarranton is back to take a deep dive into crank length with Alex. They discuss the basics of crank lengths and how changing the length of your crank arms can change your performance on the bike. Alex also gets on the indoor trainer to compare the extremes of crank lengths. Does it make a difference and should you change yours?
00:00 Intro
00:40 What is crank length?
01:56 How does crank length affect riding?
02:27 Is your crank length right?
05:18 Can changing crank length improve performance?
07:10 Comparing different crank lengths
12:30 Should everybody look into crank length?
13:06 Do different crank lengths use different muscles?
13:32 Are shorter cranks better?
14:09 Summary
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Have you ever changed your crank length? 🤓
YES!!!!
Not intentionally but by new road bike can with 172.5mm and I'd always had 170mm. Felt like it made a slight difference to my optimal cadence due to the slightly different leverage.
Yes, gone from 172.5 and 175 to 170. Better comfort for sure. Track and fixed gear cranks are mostly 165 for pedal strike reasons and I wouldn't go longer in either instance except off road.
Yes at 183cm changed to 165mm. Never going back to longer cranks
About 2 years ago, I switched from 172.5 to 170.0. That small difference in length really made a big difference in my cycling.
I’m over 50, ride a 56cm bike and live where it’s very hilly. After much research I changed my crank from 172.5 to 170 and raised my seat height accordingly. I didn’t know if it was going to be waste of time and money. As soon as I got to my first big hill I noticed the difference. It was easier on my knees and legs. Unexpectedly I actually went up my climbs slightly faster.
My knee bug me like crazy and I'm 47...getting more and more interested in a shorter crank length as a solution
Hmm🤔Only if we can ever reduce the numerals in our age. Maybe one day.
@@Musketman84th I would definitely recommend going to a shorter crank. Unfortunately you can’t just try it out. You have to buy one which is not cheap. If you’re okay at bike maintenance it’s not too hard to do yourself. You’ll need to get one specific tool to remove the crank, but it’s not expensive. Go for it, your knees will thank you! Sometimes you can find an unused one at a bike shop.
By shortening the crank length, you've reduced the torque produced by placing the force closer to the fulcrum.
For touring and hills, I have 175mm. For daytrips and quick road riding, I have 170mm. Sounds like your Willpower took you up.
@@jameslee-pevenhull5087 Not necessarily. Changes in seat position wrt the bars aren't a straight 1 to 1. By shortening the cranks, and raising the seat, OP has effectively made a very slight increase in reach, a slight net decrease in hip angle (assuming the delta in seat height here based on what the mean when stating "accordingly"), and a very slight change in the knee-to-spindle. The other side is most of us have far more gears than we actually need. So, chances are his bike absorbed the changes in gear ratio. So it sounds like OPs bike was probably just slightly too small (yes, I realize that seems counterintuitive*) and now he's got his mass more balanced centrally, and is able to leverage more into the pedal stroke without overworking his quads (here I'm assuming his knee pain is patellar rather than popliteal).
*I think its becoming pretty clear the more I see on this topic that brands are speccing crank standards way too large.
Yes, I am 5' 11" and ride a 56cm bike that came with 172.5mm cranks. I am also 62 years old.
I used to race 40 years ago, and when riding the track, 165mm cranks were standard. Obviously power and speed were no problem for all the amazing track superstars riding 165s, safety in cornering was improved a lot, and there was the added benefit of being able to breathe that little bit deeper because the thighs weren't impinging on the diaphragm!
So, when getting back into cycling 2 years ago, I decided to swap out my 172.5mm cranks for 165s, and have enjoyed riding since!
I do almost all my riding on Zwift (12,300 miles last year) with a couple of imperial centuries IRL, and have never noticed a downside. My sprints are still improving wattage-wise, so I don't think the leverage decrease from a 4% shorter radius is even noticeable, and in my opinion, is more than offset by the benefit of deeper breathing and more efficient spinning/quicker cadence.
That’s really interesting. I wonder why the trend went to longer cranks?
@@a1white Back then, a 23 tooth rear socket was considered extreme, so they were looking for every bit of marginal leverage gain with the 42/52 chainrings up front. That's my guess, anyway. I guess the original groupset manufacturer, Campagnolo, would know why the crank arm lengths were standardized as they were.
Thanks for dropping us a comment Rob! Great to hear that you've stuck with the old school 165 and that it works for you🙌
Back when I started in 1970, only the very tallest, well over 6' tall, match sprinters/kilo riders on the track ever rode even 170 cranks, let alone anything longer.
They also did not ride the 'stayer/motorpaced' size gearing that is requisite nowadays on the track, nor did they have all of the aero advantages to enable that crazy gearing, so in order to go faster, they had to spin to higher revs than today's sprinters do.
Those short cranks let them turn very high revs very smoothly.
I absolutly love bike-fit content! Keep it up.. i watch every one of them multiple times.
I switched to 165’s about 2 years ago from 172.5. I’m 178cm on a 56cm bike. I was suffering with knee pain on my right leg and this was solved from the very first ride. I ride a lot more on the drops than I ever used to.
I'm 6'1" Ironman triathlete that switched from the stock 172.5 to 165mm cranks. It made a huge difference in muscle activation, aero, less stiffness, etc. I've also ridden a bike with 155mm cranks but found that was too short and I lost power significantly.
So cool that you've experimented with different crank lengths 👀
165 metres wow! You must ride the Tsar tank... The Tsar bikea! th-cam.com/video/jfa_yuU86js/w-d-xo.html
what's your inseam or tibia length? do u think u can do 162.5 or 160mm?
What is the iron man bot cat.?
I switched to 165 on my Tri bike a few years back and it was a world of difference. More comfortable and much lower aero position. Thinking of reducing my road bikes too.
I moved to 170 from 172.5 a small change, but what I have noticed is a smoother peddle stroke i can get over the top more easily and les knee pain. The difference really stands out when i get on my smart trainer as it still has 172.5 cranks my peddle stroke is much more choppy. Great info GCN.
Recently changed mine from 172.5 to 165. Being only 5'4" 172.5 was way too long, but had to save to afford new crankset. Not tried on road yet as don't ride this bike outdoors in winter, but I had 165 on my MTB and felt comfortable with them.
Very timely for me. After 40 years of riding I had my first pro bike fit a few weeks ago. I've been riding 175s forever based on my 188cm height, but during the fit discovered that my lower leg bone is very long in relation to my upper leg bone, indicating I would do better on shorter cranks. Changed to 170 and I feel a big difference, much smoother pedaling and like the other comments below I think I'm getting more power out. Did FTP test and was better by 20w!
Nice! Good to hear
I'm 174 cm height and now I'm is process of changing from 172.5 to 170. Hope getting better performance next season.
@@gcntech Maybe we should do a science experiment on the main channel if crank length makes a difference for speed?
I, too, changed to shorter cranks a while back, nearly ten years now - previously rode on 175 and 172.5mm cranks just because that's what my first few road bikes came with. When I started to learn more about road bike fitting and read a few articles about crank length, I went down to 170, and I do believe it has saved my knees
I’m just 158cm, previously using crank length 170mm provided with the completed bike on size Xxs - xs (size 44-47cm) with top tube 50cm-51cm. After so many bikes owned previously I decided to build a bike with 165mm crank length the shortest length available for r8000 and currently using 160mm which is the shortest length on R8100 is perfect for me ❤
Am almost the same heigth and bike size 160 in 47 madone, currently 170mm crankset, was 165 or 160 better for you?
I'm 175cm tall and I ride 160mm R7000 cranks for 3 years. Raised the seat (Selle SMP Composit) by 1cm, back by 3mm. Perfect pedalling motion. 👌
Love this kind of content! I'm a smaller rider, and two fitters have suggested shorter cranks. This is really something that should be more easily accomplished than it is now. To have to replace a whole chainset to get the correct fit is ridiculous.
I'm surprised you are suggested to change the whole groupset (if I understand you correctly). you can simply change the crankset and leave the chain/rear cluster as is assuming you remain consistent with 10/11/12 tooth width as you had before
Great video! I've struggled with crank lengths for years. I'm 174cm (5'9" in old money) but have short legs (and arms) for my height. I've always been of the opinion that I ought to have 165mm cranks. Trouble is, as said in the video, bikes tend to come with 172.5mm or 175mm as standard. Even the sites where you can fiddle with the spec of a bike (Ribble, Planet X, ...) go no shorted than 170mm. A few years ago I did manage to swap out some 170s for 165s on one of my road bikes and found it much better on long and/or hilly rides, but it was expensive and a big faff. It's a great pity the bike manufacturers/builders don't take this more seriously. (And don't get me started about handlebar widths on off-the-shelf bikes!)
Riding became so much more pleasant after I changed all cranks to 165mm!
Agreed. Stopped the thighs from hitting the keg (covered 6 pack) as well...
@@Chrysalysalise more room now to enlarge the keg! 😂
I did the same, down to 165mm from 172.5mm despite being 6'3" / 190cm. A long term sacroiliac joint injury was playing up despite lots of work on flexibility. Shorter cranks have helped me keep riding without aggrevating the injury. No apparent difference in power except perhaps the initial few seconds of a sprint. Cadence is of course higher, but I do run a compact chainset with an 11-34 casette.
Really interesting post. Thoughtful and low key. More of Jake please.
My first new bike in 1985 came with 172.5. After a year or two, I changed them over to 175's. I've been using that size ever since; except I set up a Cyclocross bike with 165's.
Bike fit videos are always appreciated 🙇 I changed the crank length from 172.5cm to 170cm on my 54cm Domane when I upgraded the groupset. I think it was a good decision based on my body's flexibility and it had a positive impact on my self selected cadence. I'm a 175cm tall rider.
Great to hear we've helped you with your fit! 🙌
i have same bike, my bike fitter suggested 165mm. my current bike is trek domane sl6 2021 with 172.5mm crank
@@gcntech Always interested in bike fit videos. There is so much to learn and these provide a wealth of information.
A shorter crank length would require that you raise the saddle to compensate. Raising the saddle would give a more aggressive position.
Changed to 165mm 2ys ago and never looked back. I’m 179cm. Made it easier for me to up my cadence and get away from a bad grinding habit.
Banging video, as always. I just wished you guys had raised the saddle by 10mm when you changed the crank from 175mm to 165mm. Same knee extension, though very different angles at the top stroke. Will keep searching youtube for that comparison.
Rode 170mm cranks for years. Had knee issues for years. Bike fitter tried me on 165mm cranks on a jig and the immediate difference in feel was incredible for such a seemingly small change. No knee issues now so I will never go back. It just feels smoother over the top of the pedal stroke, even in an agressive position.
Great wrap-up questions at the end. Great answers as well. I think there's a lot of research that says a lot of things about crank length, some of it contradictory to other studies and some contradictory to our common beliefs. I agree with this guy... if there's no problem to be solved, don't mess with it. However, if you're a tinkerer, it sure seems worthwhile to experiment.
yes please, more bikefit related videos. Thanks.
Back in the old imperial days I rode 6.5" (165mm) cranks on my track bike. This helped to avoid grounding the pedals (flats with toeclips and straps) on the relatively flat bends on the outdoor tracks - I'm looking at you Preston and Alexander Parks!
Very interesting. I'm 65, avid gravel rider and bike packer. On a recent 375 km overnighter I experienced swelling in my right knee. I put it down to starting off too hard and very hilly. I'm 6'2" with 35" inseam. I raced MTB's on a 180 crank. All my bikes now are 175. After my knee issue I started looking at ways to reduce pressure on my knee. I have always adjusted my cadence to pedal a smooth round stroke around 90 rpm. I'm going to try an oval ring on my 1x mtb just for the fun of it. After watching this I'm going to try a 170 crank staying with round ring on my gravel bike. Other interesting note to Alex's comment about road riders not being in the aero position much. As a gravel bike packer I have aero bars on my gravel bike, I use them a lot on long open stretches. The 170's will let me raise my saddle and with carbon post will increase give from the post (hadn't thought of that before). I 'd always thought 175 was my "standard" . No harm in trying a 170 crank. Will be interesting to see if it helps on my long trips.
I raced a lot in the eighties, using 172.5s and occasionally 175s, with some success. Then, about 5 yrs ago, largely thanks to Australian Cam Nichols influence, I changed to 165s. Perhaps due to the smaller pedal circle, it seems that there is not as great a demand made on my heart/lungs for a given speed. I’m completely sold on the 165s!
I'm 57 1.85mts have a 33"/34" inside leg measurement, both my road bike and my touring /gravel bike are now set up on 165mm cranks and I find it perfect . The road bike is a 48/34 sub compact with 11 32 cassette this bike stays out in France and is perfect for alpine climbing. The Touring/gravel is again sub compact 46/30 with 11 36 cassette and again will get me up the toughest climbs loaded up. My flat bar hybrid has a compact 50/34 crankset with 175mm cranks and you do notice a subtle difference when you ride this and then swap back to the shorter crank. I say to anyone thinking about it drop those crank lengths you will not regret it.
Went from 172.5 to 165 via "new" bike. Very skeptical at first but the position change opened up large increases in power over 3, 5 and 20 min intervals.
The actual length of a person's legs regarding hips, thighs and calves makes a big difference.
Thank you all. I was expecting exactly for a crank length content! Please, do you recommend to use different crank lengths? I lost the left ankle movement and 4cm of the leg lenght. It will be really helpful! 👏🙌
I’m 1.78cm riding a Canyon Speedmax with 165mm cranks and I simply love it! Not only it’s much lighter on my body when running off the bike in an Ironman, but I also find it easier when climbing.
Boy I thought I was short at 173cm, but you at 1.78cm...how do you reach the pedals at all? LOL! - Cheers
I take it you are 178 cm tall but what is your Inseam length please because I am the same height but91.5 cm inseam and on 175 crank length ,just wondering if I should change to another size?
Unpopular Opinion: 165-175mm is a laughably narrow range to cover all the normal adult heights out there. We really should have something like 150-190 mm in 5-10 mm steps. Compare 165 to 175, new compare Manon to Conor and tell me we have access to a reasonable range of crank lengths.
Going back to my winter bike with slightly longer cranks I can defiantly tell the difference in the 2.5mm with how high my knees were but also muscle recruitment. If you are changing crank length be aware you may feel a difference and may need to change thins such as saddle height and also for/aft, I found that was necessary
Very interesting! Definitely want to see more videos on bike fit.
Watch Neil Stanbury bike fit videos on TH-cam.
I have a 34" inseam and have ridden 175s for decades. As I entered my 50s I experienced knee pain, the worst being at the top of the stroke. I changed to 170s and raised my saddle 5mm. This alleviated nearly all pain.
Thank your videos. It was super helpful to me and bought me a smaller crank arm❤
I recently built a new carbon bike . I bought the frame to fit me. I have 31” inseam but a very short back and largish chest . All my previous bikes had the ‘standard’ 170/175 crank lengths , with the result I could never get down on the drops as my thighs hit my chest. With this new bike i’m down to 155 cranks and it is working great.For ‘chest’ read ‘rib cage’ before there’s a quip,😉
Good information. Thanks
I’ve used 170, 160, and 165. 160 was a little too far on my tri bike, 165 works great. I’d use 165 on an mtb if I had the choice for pedal clearance. I could do 175 on the road bike too but 170 is fine. I have a 72.5-73.5 cm saddle height. I used it to get room at the top of the stroke on the tri bike it was a great benefit. Also helps the tight ankle angle at 9 o’clock on the stroke.
I used to ride with both 170 mm and 172.5 mm cranks, but when I hit 68, I started having some knee pain so I switched to 165 mm and now seven years later, I’m still riding, Had I not switched, I doubt I would still be able to ride.
Interesting, I'm 68 (bloody hell, how did that happen?) now and not in any discomfort, but reading all of the research and comments thinking it might be time to change. I'm about 178cm and have 172.5mm cranks, when you switched did you make any other significant changes other than seat post height? Did you notice the slight increase in cadence?
@@davidhinton7038 Hi, no, I follow the first rule of experimental physics, "only change one variable at a time". When I changed my cranks is only adjusted my seat height. and yes, my cadence did go up about five RPM if I recall correctly.
I've just at least 3 forums supporting crank length L(mm) = 5.48 x I(in), where l is inseam measurement.
Indeed, as 5'6" short rider with inseam 29", when I bought a bargain price road bike with a 54cm frame, I found the 175mm crank supplied uncomfortable and couldn't get aero. My chest cavity felt squashed, quickly leading to breathlessness in the drops.
The above formula gave me a ~160mm crank length and, since the smallest standard size is 165mm, left me choosing between Rotor or FSA.
There was immediate positive difference, all of a sudden I was riding everywhere like a track rider and found I could stay in the drops almost all day long. I could comfortably increase my cadence and now I'm normally the last in the group to remain seated on climbs and even when accelerating to a sprint or to catch a wheel.
Have noticed improved availability of shorter crank lengths on the market since women's pro racing has regained popularity, although the main makes are still a bit slow to snap up that market share, capitalising instead on lack of awareness.
I have since heard from a 6'+ chap in the forums who remarked that this formula resulted in a crank length of nearly 190mm! Which I guess shows that taller riders always ride 'short' cranks anyway and perhaps this is a hidden performance advantage taller riders have. I seem to recall a theory from decades ago that despite diminutive riders having clear advantage in the mountains, grand tour winners for some reason were still produced of taller riders. Claudia Chiappucci, case in point, when he came close several times without taking the cigar.
Moved from 170 to 165 and, while I felt I lost a little bit of shove on the pedalling downstroke, my cadence is higher (very comfortable in the low-mid 90s instead of low 80s before), definitely opened up my hips, and I feel like I’m doing more productive work on the upstroke of the pedalling action. That latter one is hard to explain, but overall a noticeable change and wouldn’t go back.
I have always ridden with what ever cranks were on the bike, never seemed an issue. Most 170.
I am an absolute fanatic when it come to seat height and can really feel a 1 cm difference, especially if low. Getting handlebar height correct helped with tired back, although I still get a numb left hand sometimes.
Older bikes were easy to swap a crank, but my newest bike (first brand new to me) the right crank is integral to the chain ring, so no easy swap. It is not a problem, as I love the bike as it is.
Like all things, find what works for you, then ride the hell out of it!
Couldn't put it better ourselves! Ride the bike that make you smile the most 🙌
For me at least, crank length turned out to be a surprisingly important bike fit variable. I was experiencing some fairly significant knee and hip pain, and so I moved from 175mm to 170mm cranks just to see what would happen. (I ride a 58cm bike, and am 180cm tall, so the bikes I tend to ride almost always come with 175mm cranks.) I was a little skeptical at first -it's only a 5mm change- but it was a LOT more comfortable and efficient, and the knee pain completely disappeared.
Great information on crank length, I’m over 70 years old, and have a hip replacement and I’m going to look into it
Hope it helps 🙌 great to hear you're still spinning away!
My first road bike came with 175mm. I then bought a Tri-bike and it came with 172.5mm. I loved the shorter length. I did research and it said I should be at 164mm but I have only gone down to 170mm and love it as well. Im hesitate to go down to 165mm. People used to tell me I sit to one side and my right knee sticks out. With the shorter length both those things have improved. My road bike is 52cm and tri-bike is a small.
Thanks for this nice informative video! You just talk about advantage of shorter cranks. Is there also an advantage of the longer once? Cheers
5’6” tall. both my PT and I agree that need to be on 165mm cranks. For those that ride mountain, this will cut down on your pedal strikes too. The downside is that I’m now buying a new crank set with every new bike purchase.
Good wrap up at the end.
I'm 5ft 8, all my bikes have 172.5 cranks & at the time 53 outer rings I've put on 50 rings now, I don't need such big gearing at my age (64). Would like to try shorter cranks but way too expensive . I'd have to replace 4 chainsets/cranks.
Just recently changed my crank length, from 175mm down to 170mm.. a small difference but I find it so much more comfortable.. with a slight raise in the seat, no more hip pinching and feel like I can get power on the down stroke more smoothly.
I started riding last summer - I had 175mm crankset but when I upgrade my 105 groupset to 11 speed research a bit on crankset and realized 175 for my height and weight (177cm for 78kgs) was from another era. Then 172.5 was the only available choice. Before I had some pain in the laterals ligaments by the knee cap. Not sure if it is training or the crank length or a combination of both but that pain is gone.
I feedback though is I feel I have tu push slightly harder on the trainer while starting the bike, while the resistance is very hard. So although it fits my body better it looks like It is asking my legs to develop more power
I'm looking to change my cranks for crit purposes (pedeling in corners) but after reading all the comments seems like I'm definitely going to do it from 172.5 to 165
By pure chance, all my bikes so far have 170mm cranks (two MTBs and two vintage steel road bikes). I'm 176cm long and have been riding a huge 57cm classic steel Bianchi with classic deep drop bars and 110mm stem... Absolutely way too large, but I'm used to it! Will be interesting to see what difference my new build in a much better size will do!
I used to commute on a 1964 Rudge "colt" 3-speed (the usual 26" wheels, but on a slightly smaller adolescent-sized frame) which had 140mm cranks! I have short legs (28" inseam - hence the choice of a small bike for commuting) and I normally use the 170s that come on bikes, but feel better on 165s when I can get them. Those 140mm cranks were crazy short, but honestly, for slow short utility rides, they were fine. The only time they felt like a problem was when climbing the one big hill on my daily route. 140s don't provide a lot of leverage going uphill... Conversely, the few times I got a bike with 172.5mm cranks, I developed knee pain after just a few weeks of commuting. I reckon that pain would have been accelrated and exacerbated had I been using them on longer, harder rides!
All my cranks are 172.5 simply because that's what came with the bikes (generally M/54cm). As a short-arse (171cm) maybe I could do with shorter ones, but I've managed for 30+ years. On the other hand, Q factor is more variable, and I definitely feel the difference when on the mountain bike compared to road bike
This was a very informative video/topic. I ride enough to where I can feel subtle differences in my bike set up but not significantly. My old bike had 175. My new bike is 172.5. Not sure if the power of suggestion makes me think that it's making a difference. Anyway, I never really considered the physical body aspect of crank length. Always thought it was more of a physics and leverage thing. Thanks for this! 👍
Many bike fitters and frame builders (e.g., Zinn) select crank length as 21% of the inseam. E.g., for a 79cm inseam, use a 165mm crank.
Just went to 165mm on my crit bike - usually ride 170mm on my road bike - I did it to increase cadence and open the hips more - I hope it was the right thing to do! I'm 5'7" with a 29" inseam - so, I think this is a better fit for my lack of stature!
hey bro, im same size! I have 170mm now but will be testing 165 soon. Thx for your input....Have you ever tried smaller than 165??
I 💯% reckon Ollie would notice that change. It feels a huge difference to me going from 172.5 to 170mm. I'd imagine Ollie is very tuned in to his position and feel on the bike, it would be amazing that he wouldn't feel this change.
Just went and measured the cranks on mu old old old road bike....How old is it? I got from my sister's boy friend in '74, I was just going on 13, and turned 61 last Saturday......
Cranks are 165!, I would have never guessed. The boyfriend was 6' 4", so the frames is the largest you can get. I was only 5' 6" at the time, and topped out a 5' 8" (173cm) but always love larger frames. Haven't ridden it for quite some time, so I plan to dust it off, new tires, lube and adjust tweak.
All these videos inspire me to ride more. If I get the roadie running smooth, I can shoot for a 100KM, then maybe 100 mile. I don't think I ever did do 100 mile.
I am 173cm, 50+ and overweight and was happily cycling on 172.5 all my life. I only realised there are different crank lengths when I investigated why my wife's bike felt more easy to pedal (had 170). So when I ordered my new bike I chose 170 instead of the standard 172.5 (bike brand that you can customise). Unfortunately it came with 172.5 by mistake so it had to be changed to 170 (at their expense). Same bike same day it was the moment of truth with a direct comparison before-after. The difference for me was immediately felt and totally justified my choice. Previously it felt like I was winding up some big machine, the pedal circle was too big. Yes, it soulnds like a joke or conspiracy theory that 2.5mm either way, 0.5cm smaller circle would make such a difference but it did. Less stress to knees, more space between thigh-abdomen and higher cadence that seems to suit me more.
I cannot comment on power as I have no data on the 172.5. I have not tried 165 so I cannot tell if that would be even more suitable for me but seeing how many of you tried them I will be open to try before I buy the next time. And if I can tell the difference straight away when I ride another bike with 172.5 I am sure Ollie can too.
With smaller cranks you tend to produce less torque (less push on the pedal, easier for knees and muscles) but power is torque*rpm so by increasing cadence there is no power loss. In real life you will probably go one gear easier with higher cadence for the same power/speed. And you might need a shorter gear to counteract the loss of torque in steep hills. Any difference in power, more or less, will not be due to the crank but relies on how your body works better.
Taller bikers are usually heavier so to get a similar power to weight ratio to have any chance they will need to produce more power. And once out of the hills W/kg does not count as much as absolute power that translates to more speed in the flat.
This reminded me of a story about Lance Armstrong in the tour de france. In preparation of a mountain stage (alpe d'huzes?) he had his whole team have a left crank shorter mounted on raceday than the right side. This was due to having more left hairpin turns than right handers, and gaining and advantage this way.
Anything for a distraction eh?
My Giant Defy came with 175mm cranks. It now has 170mm. Huge difference. My bike shop say they cannot understand why manufacturers insist on supplying cranks over 170mm.
TL;DR yes you can make some determination of crank length on your own.
I started out riding mountain bikes and they ALL came with 175mm cranks cause everyone thought you needed the leverage. On long days, or if it was cold, I got some knee pain but it wasn't too bad. When I started riding road, it came with 172.5 and that was a bit better, and I made more power as well. But I still didn't put it together until I tried riding the track and the rental bike came with 170mm, which felt like a huge improvement in power, like my legs weren't bent too much at the top of the pedal stroke. So I decided I had to figure this out, because as a 6'2" person with 34" inseam, I should be OK with any of the cranks I tried.
I started by measuring my leg bones, between the joints. And to simplify the calculations I assumed the ankle wasn't moving, which obviously isn't the case but it's pretty valid for comparison of different crank lengths. Using this method, I was able to figure out that 170mm was the longest crank I could use before my knee bent greater than 90⁰ at the top. This was because my femurs are about 2" shorter than they "should" be based on NASA biometric surveys that were done back in the day. You can do the same measuring and triangulation, and see what the effect of different crank length would be.
I am 5' 10" (and nearly 50 years old), and my inseam is 85.4cm. As far as I figured out, the formula for the optimum crank length is between 20% and 21% of the inseam; for me, the middle of 20,5%/175mm turned out to be the optimum (as I tend to use lower cadences, just like Bert Grabsch did). After an accident in February of 2018 (I got hit by a car as a pedestrian, with a cartilage damage as a result), I tried 172,5mm cranks in combination with higher cadences, with the idea of relieving the force on the cartilage, but in contrast (I guess due to the reduced moving angle of the knee) it felt even more uncomfortable, and increased the force on the knee, so I switched back to 175mm. In earlier years, I also tried 177,5mm cranks (Campagnolo offered its Record alloy square taper cranks from 170mm upt to 180mm), but on the test ride, the legs got tired after 30 minutes of riding, so I had to remove them again. For opening the hip angle on my TT bike (a cadex CFR converted to a tt bike by using a -45° adjustable stem), I kind of roll back the upper body backwards while keeping the back in position on the saddle ( it's a little bit like making a cat hump), and then I can feel (especially on descents), how the speed is increased more than with a flat back.
This also depends on what kind of riding you do. Most bikes are typically "overdriven", in the sense that the rider chooses gears to turn the rear wheel faster than the pedals (you can see this visually when the front gear is bigger than the rear). In this situation, a shorter crank/faster cadence would require less extreme gearing to get the same final drive speed. In the opposite situation, where the rider requires more torque at the rear wheel, a longer crank develops torque from the get-go, reducing the need for really low gears.
Most bikes have a range of gearing to deal with this, so I would look primarily at the extreme situation of pedaling a heavy bike uphill.
I'm 5' 5" tall with a 28.5 " inseam and 66 years old. I changed my crank s from 170 mm to 165mm 6 years ago. It made a big difference in my comfort on long rides. Bikes are made for the median height of the population of the country. They have diffferent size frames but factory bikes all come with the same crank size because of cost. Power is force x velocity. You compensate by spinning faster which is better for the knees. I am a retired chemist/ biochemist trained in the sciences. I'm a big fan of Ollie.
Years ago I challenged all my bikes to 170 because of knee pain. My road bikes came with 172.5 and my Mountain bikes came with 175. I’m only 5’8 with a 30 inseam. Cycling became much more enjoyable and the knee pain got much better.
Well done Alex, I do like your videos. A couple of coments:
You could usefully have measured your power and cadence with the different lengths.
Shorter cranks mean lower gears which means if you are foimg to go faster, either you must increase your gearing or pedal like a cartoon character!
Saukki on the velomobile channel made a video last year about crank length and referenced a couple of research papers which might be worth looking at. Anyone interested in recumbents should look at his channel (nice balance of fun and learning).
Reading the comments below, the bike industry has got it wrong.
went from 170mm to 165mm + oval chainring about 6 months ago, my pedal stroke is far smoother. Before I could hit 100rpm, then things got very untidy. Now I can go over 120 rpm, amd things are still smooth.
I've replaced the cranks for a shorter one in a MTB, without changing anything. Used the larger gear in the front. At first, didn't notice nothing different but was amazed when realized I've reached my destiny 7 minutes earlier.
Great video. Would like to see more bike fit videos with Jake and Alex.
Happy to move to shorter cranks and 85psi 30mm tyres so that in a few years we can move back to longer cranks and skinny higher pressure tires.
Excellent vidéo
I have a friend who is riding extrem long cranks 180 for a seat height of only 74cm it s against Theorie however he has won some 180 amateur races and was three times winner in St Johann (master World Cup) on the other side my cousin is riding 167.25 he is also excellent - he has changed from 172.5 because of problems I the haunches
I think it’s a try and error area
Thank you for the excellent video
With the appropriate adjustment to saddle height with a change in crank length the effect on knee height is 2x that of the change in crank length.
12:03 "you'd never ride like this on a road bike" 👀 lol maybe like 50% of my riding is like that 🤣
I like my 180 mm cranks. I feel like I can power them through anything and I've never had any problems with hip pain.
Same here
I have a 170mm on my ICE VTX tadpole recumbent. I switched to a 155mm crank length and got knee pain, so I switched back. On velomobiles, the crank lengths tend to be much shorter; 155mm is long and go down to 140mm.
I started on 172.5 for years and experimented with 165 and 155. My pedalling was smoother but my power output was also lower. Since then i've worked on my flexibility and gone back up to 172.5 which i currently prefer. I have proportionally long tibias. I wonder what other long-tibia cyclists prefer for bike fit.
My long tibias cause my knees to go up too high. I swapped to 165s and still find some pain in the hips. Might go 160 on my next bike
I’m 62 going on 63 and have tried shorter cranks. My 6’1” frame settled on 172.5 as the 170’s were just too short and I lost significant power. From a former cat 1 racer back when dinosaurs roamed the earth, the 2.5mm was not a big comfort change for me
As a 186cm rider I had 175mm cranks on my first bike and got a new bike lately with 172.5mm cranks. Just a subtil change, but my average cadence on my first ride was increased from 78 to 82. Still comparably low cadence, but with a higher cadence it should put less stress on fast-twitch muscle fibres...
Fast twitch and cadence are unrelated. You can have longer cranks and not be recruiting explosive (fast twitch) muscle fibers.
I'm 193cm, rode 175 for years, and went to 172.5 to follow the "shorter is better" trend...Definitely easier to turn the gears over (spin), but also had to ride easier gears compared to 175 due to less leverage and obviously rode consistently slower due to the smaller gear...Tried 180mm and put out consistently 8-10% more watts than the 175 and experienced corresponding higher average speed. I took a look at what Pros ride and noticed they have completely avoided the "shorter is better" trend, makes sense...Physics is physics, if you can tolerate the larger circumference of the pedal circle, I would definitely advise going LONGER for more power. For every 2.5mm of extra length you can push roughly 1 tooth bigger on the big ring with the same foot force...(172.5mm = 50t 180mm = 53t with same effort) - Love free speed...
I have a Trek Domane SL6 with a stock 172.5. I've never been comfortable on it, even with two fits. I bought a 50 USD State bicycles steel single speed bike with a 170mm crank. I've never been more comfortable. I'm switching the Trek to 170. If ithat doesn't work, I'm selling it and getting an ORRO.
I'm tall, 193cm/6'4" with a 91.4cm/36" inseam so I run 175mm cranks. My wife is a lot shorter and her XS frame came with 170s. I was able to find some 160mm cranks and that's made a world of difference for her. I find it a bit odd that there aren't more options for shorter cranks for women or shorter riders in general.
I have bikes with crank lengths ranging from 165 to 175, but since they're on different kinds of bikes (road, single-speed, e-bike), I can't tell any difference. I changed my drop-bar "hybrid" from the stock 175 to 170, and that did make a difference, mostly in my ability to maintain cadence on climbs. Even then, my chain ring sizes changed a bit with the new crankset, so attributing cadence to the crank length change is uncertain at best.
Im currently using a track square tapered 152mm crank , and my inseam is 71cm. For shorter people like me, manufacturer still puts 170mm crank on factory bike, that's an atrocity. My usable crank range is from 152 up to 160mm max. Now i'm not reaching for the pedal on climbs, deadzone and pedal mashing tendency gone, much more even pedaling. I do need to reduce my chainring size by 2 teeth to compensate for the gear increase. But no speed loss.
Hello! thanks for the content, very helpful. I'm changing my crank set and as a consequence thinking about buying a 5mm shorter arm. Will a shorter crank length redistribute a riders weight more onto the handle bars?
Very interesting video - thanks.
Perhaps in a follow-up you can spend some time exploring the relationship between height and crank length. I'm over 190 cm tall and have always used larger frames (currently 62 cm) and longish cranks (currently 175 mm) else I need to use an insanely long seat post.
Not just height but limb length. I have a long upper body but relatively short legs.
Height has nothing to do with it. It's leg length, and more specifically, the tibia to femur ratio
More bike fit content please!
It is well worth working with a professional bike fitter. My biking has improved in both comfort and speed. This was a couple years after buying a bicycle new with electronic set up at the beginnig. Very happy I made the investment.
Very interesting. Nearly all of the comments make me think that manufacturers should make different crank lengths available on new bikes. Normally there is no choice with a "standard" 172.5 all that is offered. Online retailers like Ribble are much better placed to be flexible in areas like crank length, stem length, handlebar width, cassette range etc. Difficult for your local bike shop to match this flexibility. I ride an endurance bike with 50/34 chain rings & these are too big for me...I'm old & slow! It would be nice if there were more sub-compact options available - see A Path Less Pedalled for more details
Many recumbent riders have found that shorter cranks as short as 145-150 mm but also 160-165 mm are optimal for reducing knee bend and providing optimal power output. When reclining back on a recumbent, the fit is obviously much different than upright. If looking for quality short cranks look for manufacturers that sell “short cranksets for recumbents”
I‘m 183cm tall but with a long inseam of 90cm. I‘m using 175mm cranks and already ride at around 93rpm. My take is that if I used shorter cranks, I would have to put my saddle even higher and have even more drop to the handlebars and I would have to ride at closer to 100rpm for the same power and maybe have a less efficient pedal stroke.
Yes, your saddle will be higher. But with a shorter crank you'll be able to rotate your pelvis forward and flatten your back, creating a more aero position.
I'm 6ft1 moved to 165mm crank with oval rings and will never look back, so comfortable and climbing so much easier. I'm very big at 112kg.
9:05 "Oh these hips don't lie Jake"🤣
Great information. I'm a very short legged 170cm and my knees are always hitting my chest when I get low. The shorter crank changed all this and is much more comfortable. Smaller bikes and shorter cranks make sense. Why would my bike and Connor's have the same crank length??
I am 6’1” and I have been on 172.5 for the last 23 years. Given that the DuraAce group set I got on my last bike was several thousand pounds, I am sticking with what works. I would try shorter cranks if a bike fit recommends it with my next bike in a few years, but I am sticking by the rule that says to avoid changing position if you have one that works.
Matherose, I'm no expert but I read a ton of content on this topic. At 6'1", the 172.5 may already be the ideal shorter crank for your size. I'm 5'9" riding 172.5 which I like. Used to use 175 and wonder how the 170 would differ. I won't be making a change though.
More fit vid plz. I think it would be great do a video on bar height and break the myth of lower is faster
Swopped to 165 from 172 after my Dura Ace cranks split apart on drive side - went with rotor so have a full set now with road and TT and tri bikes - shorter cranks opens hip gets you lower/aero and as long as you don’t go silly with shortening (i could run to 160 on TT but it’s £££) crank lengths to say 150 - oh and as a mtb rider too with modern geometry lower bb’s shorter cranks = less pedal strikes and it’ll save your hips all round ‘ WIN
A surprising benefit of a shorter crank on a mountain bike is increased ground clearance - less chance of the pedal hitting something.