Crank Length - A Bike Fitters Advice

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#cycling #bikes #bicycle

[thompson]

One thing I've learned from these videos/going to a bike fitter: the fastest bike is the one that fits you best. Thanks for breaking down some of these trends.

[danielhall]

In the past though, crank length seemed to correspond to the rider's style, their peddling, and where they liked to sit on the bike. I'm 5'7-5'8 and I should be on 160-170mm cranks, but I hate the spinning feeling of a crank shorter than 170. In fact, 170 bothers me somewhat because of the smaller circle I have to pedal, which is usually the selling point. I peddle with a classic heel drop before reaching the top of my stroke, I can't stand the lack of leverage with anything smaller than 172.5. Also I find that a shorter crank makes me feel like I'm on top of the bike, which really changes the handling, I like the feeling of sitting inside the bike's cock-pit, which feels more responsive, which is where slightly longer cranks put you. I find a medium-long crank, 172.5, to be the sweetspot for a heel drop peddling style, which usually corresponds with a slightly lower saddle and more set-back. Also road bikes seem to come with higher bottom brackets than they used to, so a shorter cranks seems to put the rider extremely high up on a medium sized and up bike.

[JakeMay]

Great to see how much James cares about this stuff and making cycling inclusive for more people

[Ugoeh]

Hi, your comment about functionality of the rider is, of course, spot on. I'm 6'2", 35" inseam. My bikes come with 175s. I started with 170s 9 years ago, 165s 5 years ago. But the first crank I could pedal efficiently (round, steady pedal stroke) was 155, which I put on 3 years ago. My acceleration, speed and endurance improved 50%. I climbed everything 4 gears harder, and doubled my daily mileage over a few months. I've been riding since the 1970s. I have about 1500 hours on 155, 140, 130, 137 and now 145. My useful powerband on 165+ runs from 65rpm to about 90. My useful powerband on 145s runs from 50rpm to 100+. I can pedal as hard as I want without cramping, for hours. I size cranks by powerband, the same way a motocrosser is sized: A 450 is all bottom end, a 125 is all top end. 155s are like a big bore dirt bike, 135s like a 125. And the 155-135 range, for me, are the only ridable sizes. Thanks for all of your work, it's really helpful!

[wesleyspencer]

I ride 172.5 dura ace on my road bike and 165 on my fixed gear and I would definitely shorten my road cranks if they weren't so damn expensive and I have a power meter in the spider which is another road block. Awesome video!

[Sassonian]

I'm 2m tall - and have a custom built Zinn cycle that has 210mm cranks. Lennard Zinn designs his bike around proportional crank length and specialises in bikes for tall and short riders. Complete game changer for me. When I got this bike I jumped two groups in the local racing I was doing and that year got the most improved rider award - because I just improved so much - and it was all due to the bike and position. Zinn Cycles has custom-length cranks for sale. My mountain bike has 175mm cranks and I don't have a problem going back and forwards between the two. My TT bike has 172.5 and I think that's too short for me. But I'm experimenting with what I can do there (I only ever ride flat TT's). But my road bike with my 210mm cranks just lets me get over the top of gears that I couldn't before. Means I can hang on on small rises that used to spit me out the back of the group.

[tbGTR]

I had a bike fitting with James a few days ago off the back of this channel (cannot recommend going to see him enough by the way). I feel I almost could have inspired todays topic! I'm a 5'7" male new to road riding. I was having a lot of issues based off the fact my right hip was so tight and I was struggling to get my body comfortable. After James worked his magic on 100 other things (which all helped)...we ended up going down to 155mm cranks and that totally sorted any issues with my hip. As the video says it's all about what YOUR body needs not some study on professional athletes. Do yourself a favour and go see him!

[albymedina]

Thank you for commenting on this subject.
Crank length looks simple for many, but I find it to be very complex and relative.
87, 5leg inseam, 1, 82 height. I’ve been riding 175 and 172, 5 when I was 15 years younger, fairly competitive.
Now, with less hip mobility and plenty of hours sitting on a chair, I have been using 165mm indoors for two years, and somehow helped at first instance to open the angle of the knee, but it does not necessarily mean it will allow to handle more torque.
Recently I’m back to ride more and more outdoors and I notice that having short cranks it makes the bike way less stable when standing with harder gears. I can’t pull the pedals back in the same way I used with 175-172, 5, and it’s harder to stabilize feet and activate glutes or hamstrings properly. Too short I guess. It is very tricky to switch from 175 to 165mm for example, and what I thought would be an advantage, lately it became handicap. Ideally, in my opinion regarding what I have learn testing different cranks, I would not move anything on the fit at first instance, specially for riders who are very sensitive and have round pedaling form.
Personally, when changing cranks, I would prefer to keep same fit and keep BB within the same pedaling spot, so we are just simply reducing the circular movement, which already is a big change. Then apply tiny adjustments
Personal reference, biggest crank possible according to individual’s measurements, and be able to handle high cadence when needed. A proper fit with 172-175, to me it should allow a big range of cadence, and allowing to apply big torque at the same time, with higher torque when necessary, which somehow I do not find productive having short cranks.
Yes with 1cm shorter cranks you can raise the saddle by one cm, and you get the same leg extension, and you also feel like wow! “I feel like I was raising the saddle 2cm with my old 175mm cranks”…. “Now I feel more strong sitting in the saddle”… “Now I feel I can give it more torque”… well it probably allows to apply more torque by opening the knee angle at the top of the stroke, but more torque you will need to move the same gears which at the end affects your knee in a different way. Also, switching to 1cm shorter cranks, it changes the setback by 1 cm, but if you move saddle backwards by 1cm to compensate then the leg which is placed backwards when crank is in horizontal position, feels like you have moved the saddle 2cm backwards, so you can’t pull the pedals back the same way you was able to do it before, so with a tiny change on the saddle setback and height, the dynamics of the pedaling stroke might change radically

A tiny less than the biggest crank I can ride comfortably, will be my next choice. Back to 172, 5. It is very relative and it depends on each individual .
Wow… what a mess

[yisraels]

As a shorter guy, I replaced my cranks with 165mm what an improvement. I wish I could have found 160. What REALLY ticks me off is that even when factory ordering very high end bikes. It is almost always impossible to choose crank length. I have been looking at several bikes with Ultegra range groupset I can choose stem length, handlebar width.. different seat options, wheel options... But the basic option of choosing the correct crank length doesn't exist...

[mcat]

I’ve learned so much from these videos. I’m 5”4 with 28 in inseam. I road 165 cranks for many years. Despite three different fittings, I could not get rid of low back pain, knee pain, and some subtle bouncing on the saddle at 90+ RPM’s. I ordered Ultegra 160 crankset. I waited 8 months for the crankset. Once installed, at least 90% of my back pain is gone and no bouncing on the saddle. Knee pain reduced similarly as well. The shortened cranks helped with what I’m pretty certain is a right hip impingement. Short, appropriate cranks have helped with all of this.

[HKRoad]

I’m 178cm and ride 165mm cranks. I’m much happier with this. No knee pain - but was reluctant to change initially. So I think this shows the value of a good fitting. This has overcome major knee issues.

[HanOfGod]

Yup. As someone who is has odd body measurements, I'm 5'7 but have a very short inseam, my 170mm cranks are too long (on a Small sized bike) for me. So after a bike fit (at Bicycle 😉 although not with James, but his equally capable staff of fitters), a 165mm helped a lot with my cadence and power and a lot smoother pedalling motion than before.

[kyzersoze]

I tried 165mm and I absolutely did get the feeling of falling off the front. James definitely speaks a lot of sense and I like how he isn't sensational about one particular type of trend i.e short cranks. In the end I had to move back to 175mm cranks. As someone 5'9 with a relatively long inseam even 170mm was too short.

[oscarcraig]

Ive been absolutely binge watching all of your stuff and i got a bike a few weeks back and loving it so much thanks for making high quality videos love it

[johnlowkey]

5'7'' (barely), 30" inseam and my 54cm touring bike came with 175mm cranks. My two most recent rides (60mi and 70mi) gave me terrible knee pain and I've been going down this crank length rabbit hole. Pretty much the exact situation you described at 3:20. Ordering a 170mm crankset once they are back in stock (all my other bikes are 170mm, never had knee pain). Thanks guys!

[edmundas]

I'm 188 cm (6'2) and on my old XC bike I have 175mm cranks and I always felt like pedaling circle is too large and my comfortable cadence was 70-80 rpm, so on my new road bike I went for 165mm cranks. I feel no difference comfort vise, but now I can go ~90 rpm consistently, higher rpm reduces pressure on my knees and shorter cranks allows more comfortable low aero position.

[erics]

Overall, a more sensible discussion of crank length than I've seen from many other sources on the internet. Shorter cranks seem to be the fad right now. They may well be an improvement for many people. Especially smaller riders who are constantly given the short end by the bike companies, although, in this case, the long crank.
Personally, I don't want to spin in tight circles. If that works for some folks, good on them. I suspect many riders are more affected by their choice of gear than their crank length. I see comments here about people improving their cadence speed by switching to shorter cranks. How about just shifting down one gear and training to spin at a higher cadence?
The other problem that I see with many cyclists seems to be this ingrained belief that they should always stay seated. Somewhere along the way I suspect that they were told that it was more aerodynamic and more efficient. It is also harder on your knees to have that tightly circumscribed motion without a break. Watch the pros. Even though they have trained to stay low and aero, when given the opportunity, they will take short breaks of standing on the pedals to stretch out the ham strings and glutes.

[pmcmpc]

I'm 186cm with 94cm inseam. Moved to 165mm and it's a significant improvement over 170. I don't have much hip mobility so it's good for me.

[FrankMOrtiz]

160mm 105s have worked out for me. Leg length and height aren't the only key variables. To indicate as much is straight up group-think defined.

The ratio of tibia to leg length was, for me, the determining factor.

BTW, YouTuber Peak Torque covered this from a mechanical engineering perspective over a year ago.

[yiy]

Living in Taiwan, I easily got a Croder(MIT) crankset. Had been using a 140mm one (I do have severe hip impingement (checked)) for a while and felt awesome with it. Average 95 rpm rather than 75 with a 165mm. However, 1. It may be that the two bottom bracket holes have a bad concentricity (giant TCR advanced 2016) that the spindle had significantly different wear 180°-ly. Or 2. the spindle is not made with good enough tolerance or hard enough material (howbeit it says 7075 T6, hence may not be the problem) that the non drive side crank came up with a teeny tiny gap which ended up creeking. I've changed to a 150mm gossamer pro from FSA.