So, you are thinking of going to shorter cranks. here's what i think.

Discussion in 'Cycling Equipment' started by Rock Creek Rider, Jan 20, 2019.

  1. Rock Creek Rider

    Rock Creek Rider New Member

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    My current inseam measurement is 36" (it gets shorter as you grow old). For most of the 59+ years I've been riding, conventional thinking was that I should get long crank arms to take advantage of my long legs. The thinking being that longer crank arms give you better leverage, and they do. On the four bikes I currently ride, the shortest cranks I have are 177.5 mm and the other three are 180 mm. I've used cranks as long as 195 mm (Zinn).

    Current thinking is that shorter cranks are more efficient and you can even produce more power with shorter cranks. The reason being, it's better to spin faster in a lower gear with shorter cranks than it is to push a big gear with long cranks.. My own personal experience has been that longer cranks make me faster in some situations, but are more tiring on long rides. So, I might want long crank arms to ride up Flagstaff, but shorter ones to ride a century.

    So, should you go with shorter cranks or not? Here's my thinking, if you have a mountain bike or a touring bike set up with triple crank,, I'd probably go with shorter crank arms. But most road bike set-ups have limited gear range and a limit on the largest cog you can use. You might not be able to find a gear low enough to spin with that short crank. If you are constantly wishing you had a lower gear, don't go to shorter cranks. You might even want to consider longer cranks. If you are mostly doing long rides over rolling hills, shorter cranks might be the way to go.
     
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  2. BrianNystrom

    BrianNystrom Member

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    I've got a 35" inseam, so I'm similar to you in that regard. I've been riding 175mm cranks since the late '70s. I can comfortably spin them at 110+ rpm if need be and typically average around 90 rpm over the course of a ride. I find that I'm more efficient at a lower cadence when climbing in lower gear and a higher cadence when turning bigger gears. I've tried climbing at a high cadence; it doesn't work for me and I doubt that shorter cranks would make any difference.

    That's just the way my body works. There's so much individual variation that there really is no way to say for certain what will work for any given rider. The only way to know is to experiment, but unfortunately it's expensive to buy cranks in different lengths in order to test them. A good bike fitter can provide different cranks lengths and power measuring ability, but it will change as your body adapts to a change in crank length, so any initial measurements would be suspect.

    What I have currently has worked for me for more than four decades and I really don't see any point in changing it, especially since I don't race. It's pretty obvious that the standard crank lengths work very well for the majority of riders. They may not be the absolute optimum length for a particular individual, but I think it's safe to say that they are close enough for anyone who is not trying to squeeze out the absolute maximum efficiency. A good bike fit and quality miles will likely make a much bigger difference than a crank length change for most people, myself included.
     
    #2 BrianNystrom, Jan 26, 2019
    Last edited: Jan 26, 2019
  3. ACyclingRooster

    ACyclingRooster New Member

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    When I was in my middle/late teens I rode fixed wheel everywhere I went,I rode a 19.5" 1937 Hetchins curly and most of the time I was riding a 108" fixed gear (52+13) but would revert to a lower gear in the winter time (circa 78" as I recall).
    I am 4'10" tall with an inside leg/seam of 23". My daily commute - 6 days a week with a traditional duffel bag slung over my shoulder that contained my change of kit.
    I rode 170mm cranks and developed calf muscles like the biceps on a weight lifter and with thighs too match.
    The Hetchins was sold on in March of 1967 after getting married and not having room for storage (IDIOT).

    As I got older and having had a total left knee replacement I was not able to push a 108" fixed gear on my then 50cm Fuji track and settled for a 78" gear.
    The Fuji later became a Fixed Gear Flat-bar Hybrid that was very quickly able to be returned onto dropped bars.

    The use of 140mm cranks allows for easy spinning now that I have only two bikes left and both on Campagnolo.
    I have my 51cm Steve Goff and a 50cm Bianchi both built-up from naked frames.
    At 73 years young I am taking a more leisurely view of my cycling years that may be left and may end-up with just the Bianchi !!
    DSCF4247.JPG DSCF4341.JPG
    010520121080.jpg 020920121124.jpg
     
  4. BrianNystrom

    BrianNystrom Member

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    Someone your size should be riding shorter cranks. My girlfriend is similar in size and rides 165s. Your 140s are unusually short, but if they work for you, that's all that matters. BTW I like your tag line and I couldn't agree more!
     
  5. ACyclingRooster

    ACyclingRooster New Member

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    Hi Brian. The only reason that my cranks are 140mm is because of having had a total left knee replacement back in November of 2010 and finding that I could only achieve a ninety two degree bend at the knee and with regular 170mm cranks I could not get the full circulatory action.
    I set-up a diagram on my drawing board and concluded that the only way forward was with 140mm cranks (Thorn from SJS Cycles),they are actually Stoker on a tandem albeit there are other lengths available.
    Both of my bikes on on the 140mm cranks with Stronglight Triples.
     
  6. bijanabedian

    bijanabedian New Member

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    thanks for this forum and your comment
     
  7. BrianNystrom

    BrianNystrom Member

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    Knowing this definitely helps to put your choice in context. It certainly makes a lot of sense and it's the logical choice given your physical limitations. Keep on rollin'!
     
  8. PoorInRichfield

    PoorInRichfield New Member

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  9. ACyclingRooster

    ACyclingRooster New Member

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    Hi PinR. For some reason the sound is not being transmitted on this video but from the subtitles the conversation would appear to be pursuing the notion that short riders need or would benefit from shorter cranks - surely that is really quite subjective and dependant upon the calf/thigh muscle structure of the individual.
    For the various theories to be put to the test it surely would need crank length and chain-ring tooth count also to be considered.
    I would think that anyone doing uphill racing would benefit from longer cranks given that the tooth count remained the same when a shorter crank was selected - after-all the longer crank would mean less effort (leverage) needed.
    I am not at all aware of any real additional effort with my 140mm cranks (chosen by necessity) but there again I have taken into account the tooth count when doing my gear calculations/tooth count of both the chain-rings and the rear sprockets.
    I am currently riding my Bianchi on a 46:38:26 with a Campagnolo 10spd cassette and my Steve Goff on a 46:36:24 also with an identical Campagnolo 10spd cassette.
     
  10. BrianNystrom

    BrianNystrom Member

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    Perhaps what you need to do is to multiply the gear by the leverage ratio of the crank to get a direct comparison.
     
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