Crank length

I’ve read so many comments in this forum about what length crank to use on which type of unicycle. Very informative. . . but also very confusing!

Since I haven’t officially learned how to ride yet, I have no plans on buying another unicycle, and as far as I can tell, the 152s on my Sun 24" are just fine for me for now. But for future reference (since I’m pretty sure I’ll be interested in a Coker eventually), is there a general rule of thumb on crank lengths? Like, “get shorter cranks for trials, longer for distance,” or, “get long cranks for more power, shorter cranks for speed,” or, “get cranks that are the same length in mm as your height in cm,” or, well, anything?

I’ve been a two-wheeled cyclist for many years, but never changed the lengths of my cranks. Seeing all the comments about crank length makes me think I should give more thought to them on all my wheeled machines!


You don’t need to change crank lengths on bicycles because you can change the gearing. For unicycles, this topic has been covered ad nauseum for years, so if you want to dig around using the search, you can find tons of information on this. Even enough to build up general consensuses on what should work well for the majority of people! Granted, that’s the hard part… :slight_smile:

i hate the “use the search” reply

ok RichVoice you have it pretty much right, with your cranks for power = longer, speed = shorter… etc

id say you dont have to change them if you like them the way they are.

if you wanna have more speed enstead of power(like for a coker) then get shorter cranks like 140mm or 125mm, if you want more power for hills then get longer cranks like 165mm or 170mm and up. 152 like on your sun 24 are pretty much neutral in the crank world. They are on borderline for speed and power, id say keep with them unless you want more speed or power.

should we ignore the wealth of useful info that has accumulated over the years?

Right, well, I figured I’d covered why I was posting instead of searching: I mentioned that I’ve already read quite a few comments. But what I’ve read was more along the lines of what someone uses on their particular unicycle, rather than why a particular length would be better for a particular task. Of course, I’m sure there are posts out there which argue one way or another, so mea culpa for not searching more, I certainly don’t want to ignore information posted previously.

Glad to see you’re posting, John, I guess my e-mail got caught in a spam filter.

Thanks for the general clarification, musketman. If I ever graduate to a Coker, I’ll keep the general rule in mind.


The general rule is that shorter cranks let you spin faster and smoother (your feet inscribe smaller circles), and longer cranks give you more leverage (important for MUni or climbing/descending very steep hills, or Coker riding).

In general, I would say that I try to ride with the shortest crank length at which I can comfortably control the unicycle, given the equipment and terrain I’m riding on. For road riding on a 24 or 29, that means 125mm, only because I don’t have shorter cranks. For off-road, 125 is still OK for fire roads that aren’t too steep, but 150 is more reasonable in most contexts, and 170 in many. (I’m personally debating right now between a light 24" MUni with 150mm cranks, and a heavy 26" MUni with 170mm cranks. I’ve been riding the XC more often, if only because walking it up unrideable terrain is a lot less work).

what I’ve found is that longer cranks are not neccessarily the gateway to more speed. I can spin about as fast on my 165s as I can on my 110s. However, the effort required to do so is much less on the 110s. The ‘cruising speed’ is also higher, I guess. If you think that you might need more leverage, don’t be afraid of long cranks, since they don’t really limit your speed, they moreso limit how long you can keep the speed up for.


There is no single general rule, but there are many rules of thumb.

You have five variables: the diameter of the wheel, the length of the cranks, the section of the tyre, the skill of the rider, and the preferred style of riding.

Of these, it is easy to pontificate about the first three, rather than working on the fourth and developing the fifth!

The benefit of short cranks is that you can spin them faster. Your feet (and therefore your ankles, shins, knees and thighs) have less distance to move to complete a revolution of the wheel. That means you can ride faster, and also more smoothly.

The benefit of longer cranks is that you can apply more toque (turning force, or “leverage”) to the wheel. This is useful on hills - especially on descents where the extra confidence you get from long cranks is a real benefit.

However, it is not just a simple matter of choosing a perfect crank length. The ratio of the length of the crank to the size of the wheel is also important. Very crudely, a 20 inch wheel with 5 inch cranks will behave very similarly to a 24 inch wheel with 6 inch cranks.

However, this is only true in “ideal” circumstances on a smooth level surface such as a gym or hockey court. The big wheel will always be better on uneven ground and long fast journeys. The small wheel will always be easier to control in tight manoeuvres.

There is a secondary effect that a large wheel (especially a heavy one) has a flywheel effect, and will tend to smooth out your pedalling, meaning you can get away with longer cranks without getting into that horrible bouncy style that can come with trying to ride too fast on a smaller wheel.

On the other hand, on a bigger wheel, you “tend” to do faster straighter riding, so for a lot of the time you can get away with a shorter crank than you might think. See - conflicting advice already!

Until you can confidently freemount and idle, altering your cranks is not a brilliant idea. You would be modifying your unicycle to suit an undeveloped riding style. In turn, this would hamper the development of your riding style.

As a near beginner, struggling to cope with my 26, I fitted extra-long cranks. Hey ho, it made it easier for me to freemount, but I later found I was using a very very poor freemounting technique. Once I corrected this, I found that not ony could I go back to shorter cranks, but I preferred them - and they made freemounting easier!

There is a safety element too: a uni at high speed can be difficult to stop under control with short cranks. A Coker or 28 can take 5 or 10 wheel revolutions or more to stop. Shorten the cranks and this effect is magnified. It is generally considered a bad thing to fall off the back of your unicycle at a junction, cracking the back of your head and firing your unicycle torpedo-like at another vehicle.

Many people fit short cranks to achieve speed, but what is speed? It could be:

  1. Top speed on the flat.
  2. Average speed over a ride with obstacles and changes of terrain.
  3. Cruising speed on average terrain.

Fit super short cranks and you could find yourself with a high top speed that you never use, and you have to slow down well in advance of obstacles, and walk some of the hills, so your average speed over a journey falls dramatically.

As a very rough rule of thumb: if you want to ride far and fast, choose the shortest cranks that you can comfortably idle with. Any shorter would be counter-productive.

As a rough rule of thumb, for MUni, choose the longest cranks you can comfortably spin for short periods. Sometimes you need high rpm in a burst, either to get up a short rise, or to spin out on a descent too steep to ride down under complete control.

Another rough rule of thumb: change crank length about 1 size at a time - don’t go from 150s to 102s just like that. Give the new size time to “bed in” so that you are comfortable with them. Don’t be afraid to experiment.

Have fun. That’s why we do it.

No mea nothing.
Your’s is exactly the kind of post that I’d like to see more of. Someone with a question does a search, finds some info, mulls it over and then asks an informed question. This is the kind of post that leads to the ongoing discussion about existing topics that’s been mentioned in the other ‘search vs sticky’ discussion going on at the moment.

Besides, if you never asked, you might never have heard about the Footspeed Hypothesis
(Just for a fun bit of reading.)

To me it always seems a bit off-putting. “We’ve answered this question enough times already. Go find it yourself. Talk to us when you’ve got something new to say.” It takes a lot more effort on RichVoice’s part to dig through the 317 threads that come up in a search for “crank length,” looking for one that has the information that he wants, than it does for any of us to just answer his question. Besides, now whenever someone else dutifully searches for “crank length,” THIS thread will come up in the results, and as long as it’s in there, it might as well contain helpful information instead of just telling the person to search again for what they were already searching for in the first place.

Longer cranks for power, shorter cranks for speed, essentially. Most would probably consider 152s a bit on the long side for a 24" uni, except maybe for a MUni, which your Sun is most likely not. I’m more into control than speed myself and I tend to like my cranks a bit longer than most people do, but even I have only 140s, and that’s on my 29. For me 152s are about right on a Coker. It’s mostly a matter of your own preference of course.

Wow. Now there’s a wealth of information! Thanks for the tips. When I’m ready to buy my next unicycle, I’ll have lots of information to rely on when it comes to the cranks! Not being a speed demon, I suspect I’ll always prefer longer cranks.

And no, my Sun 24" is not a MUni. Thank god.:slight_smile:


yes we should, and put new wealth up.

out with the old in with the new!

Just to add my bit to what has already been writen:

Another variable is the rider’s length of legs and general height. (I have very short legs and even the 140 cranks on my onza 24" feel like my knees are going to hit my chin. With the longer cranks that came on it, it was almost impossible).


Yet another $.02…

I think that functional leg power of the rider is a biggy when discussing crank length. I ordered my 29 as my first uni, with 150 mm cranks. Once I was able to get up on the thing and ride, I felt like I was dismounting just because I was feeling my legs blow out after 100 yards or less. Sure, I wasn’t sitting in the seat, but I decided that I should try longer cranks until my legs got stronger. New 170’s worked great for me. I still had to learn to put my weight on the seat, but I was riding instead of walking because my legs were toasted. After a couple months my legs seemed much stronger, and I decided that I was being held back by the 170’s. I have since gone back to 150’s. Someday I will go to 125’s, if for no other reason than to check them out. But when I was a newbie with feeble legs, the 170’s worked great for me.

Follow your nose and experiment. One can learn all the lessons in any order - they all add up in the end.

PS: Gilby, thanks for the encouragement to posters that have done some searching on the topic of their question. I enjoyed hearing your thoughts on the matter.