Crank length

Discussion in '' started by RichVoice, Jan 7, 2006.

  1. RichVoice

    RichVoice Guest

    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

    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


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  2. johnfoss

    johnfoss Guest

    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... :)


    John Foss
    "jfoss" at "" --

    "Idiot America—where fact is merely that which enough people believe,
    and truth is measured only by how fervently they believe it." --
    Charles Pierce, in Esquire Magazine
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  3. musketman

    musketman Guest

    johnfoss wrote:
    > 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... :)

    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.

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  4. boo radley

    boo radley Guest

    musketman wrote:
    > i hate the "use the search" reply

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

    boo radley

    "plus Maxxis tyres suck... a tyre made of cheese will last longer"

    "no really, are you sure you love me more than your unicycle?" -my gf
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  5. RichVoice

    RichVoice Guest

    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.


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  6. tholub

    tholub Guest

    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).

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  7. flyer

    flyer Guest

    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.


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  8. Mikefule

    Mikefule Guest

    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

    Have fun. That's why we do it.


    "The good life is the life inspired by love and informed by knowledge."

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  9. GILD

    GILD Guest

    RichVoice wrote:
    > 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
    > so mea culpa for not searching more

    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
    'Constant' ( 'Footspeed'
    ( 'Hypothesis' (
    (Just for a fun bit of reading.)


    'three short gs and a long e-flat™'
    ( - 'map'
    'harper' (
    'NAMASTE!' (
    'Dave' (
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  10. weeble

    weeble Guest

    boo radley wrote:
    > should we ignore the wealth of useful info that has accumulated over the
    > years?

    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.


    To avoid danger of suffocation
    keep away from babies
    and small children
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  11. RichVoice

    RichVoice Guest

    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.:)


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  12. musketman

    musketman Guest

    boo radley wrote:
    > should we ignore the wealth of useful info that has accumulated over the
    > years?

    yes we should, and put new wealth up.

    out with the old in with the new!

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  13. cathwood

    cathwood Guest

    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).



    'Of all tyrannies a tyranny sincerely exercised for the good of its
    victims may be the most oppressive - C.S.Lewis
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  14. Icycle

    Icycle Guest

    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. Once I
    started to do many things better while riding, I decided that I was
    being held back by the 170's, and I have since gone back to 150's.
    Someday I will go to 125's, if for no other reason than to just 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.


    The path to enlightenment is shorter on a unicycle
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