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  1. #1
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    Crank Length?

    I'm 6'2" with a 32" inseam. In the past i have always run 175mm cranks. What are everyones thoughts on crank length for single speeds? Is there an argument to run shorter or longer arms?

  2. #2
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    I like longer. I am also 32" inseam. I have a FS geared bike with 180mm and love it, unfortunately not my SS. My SS is 26" wheel on the rear with 32X18 gearing. I am not the fast cadence guy, but like to push.
    It is a mixed bag apparently, but then what isn't on this forum.

  3. #3
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    there are plenty of threads covering this topic if you search.

    longer cranks give you more leverage which effectively changes your gear ratio. so you could just use a lower gear ratio and accomplish the same thing. within a "normal" range, it's personal preference.
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  4. #4
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    Quote Originally Posted by *OneSpeed* View Post
    there are plenty of threads covering this topic if you search.

    longer cranks give you more leverage which effectively changes your gear ratio. so you could just use a lower gear ratio and accomplish the same thing. within a "normal" range, it's personal preference.
    This isn't quite right because it doesn't factor torque, which is improved with a longer crank / higher gear compared to a shorter crank / lower gear. Longer cranks allow me to keep traction when the going gets really steep.

    I've been riding long cranks (185mm-202mm) since '94. Inseam = 36".
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  5. #5
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    I have had both 170 and 175. I have 175 now but not necessarily because I like it better. I could tell a slight difference but not much. I think shorter crank arms may be easier on the legs over long rides but longer armes gives more power. Either way the difference is small. I would go 175 again because I am use to it but I also liked the ease of 170.

  6. #6
    Oaktown Honkey on Strava
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    I had a bike fitting a few years ago, 165 is the proper size for my measurements. I use 170 cranks for road bike and full suspension Mt Bikes. I use 175 for Single speed because it gives me a mental edge, that I can overcome power shortages.

  7. #7
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    I am 6'1"- ish w/ 32" inseam and run both 175mm and 180mm cranks on single speeds.

    I don't notice a much of a climbing advantage with 180's compared to 175's (and run more stout gearing than my other SS riding cronies). I do notice the that longer cranks are not better for all-day rides where more spinning typically occurs.
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    Ride the length that fits you properly, I doubt you'll notice any difference at all. In fact, if a shorter crank fits you better you make actually feel more powerful like i do. And even though most climbing on an SS is done standing I don't notice any difference in leverage.

    Check out Sheldon Browns Gain Ratio calculator to make any gearing adjustments if at all needed. It takes account for overall tire diameter and crank length.

    Getting the proper crank length has been the single biggest benefit for my cycling fit period.
    Pedal through it!

  9. #9
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    I am using 170mm. On my road bike is 172mm. I prefer shorter because I can spin faster. With a longer crank, you may need to use more energy to get your pedals over in order to clear some technical sections.

  10. #10
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    in technical riding, how often do you barely hit stuff with your pedals? i could see going longer for leverage and to engage hips, but this is what limits my crank length.

  11. #11
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    Inseam = 36"
    Definitely prefer 180, especially for standing climbs. Would NEVER get 175 for SS.

  12. #12
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    Quote Originally Posted by Cygnus View Post
    in technical riding, how often do you barely hit stuff with your pedals?
    Too often. My worst crash was due to barely clipping a rock. I'm trying to minimize pedal strikes, within reason. Otherwise I'd want some 185 or 190 cranks.

  13. #13
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    Quote Originally Posted by Ryder1 View Post
    185 or 190 cranks.
    Crank length is not a problem for the most of the trails I have access to. Is Zinn the only maker of cranks over 180mm? I'm 6'5" and so far longer feels better.
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  14. #14
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    http://www.bikesmithdesign.com/Short_Cranks/crank-length-and-power.html[/url]

  15. #15
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    Quote Originally Posted by ladljon View Post
    http://www.bikesmithdesign.com/Short_Cranks/crank-length-and-power.html[/url]
    Every study on crank length I've ever seen that claims short cranks afford more power is done with road bikes. On roads, where grades are controlled, surfaces are smooth and spinning is key. I've come to believe that people who have not ridden extra-length cranks off-road long enough to personally experience their benefits simply cannot know, much less understand, their benefits. Those benefits come through torque, not power.
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  16. #16
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    Quote Originally Posted by Sparticus View Post
    Every study on crank length I've ever seen that claims short cranks afford more power is done with road bikes. On roads, where grades are controlled, surfaces are smooth and spinning is key.
    I've seen mixed results among studies, but IIRC, some evidence suggests longer cranks are better for long-femur riders. Incidentally, I've been riding a road bike the last few weeks. It has 172.5 cranks, and I'm OK with it because of all the seated spinning. But I would HATE it for off-road SS.

    Quote Originally Posted by Sparticus View Post
    Longer cranks allow me to keep traction when the going gets really steep. [...] Those benefits come through torque, not power.
    What do you think the benefits are? More low-speed torque? Or more precise application of torque at low speeds? Both? I imagine 130 cranks would be very clumsy for applying high torque at low-speed.

    Are "spinners" more likely to prefer long cranks than "grinders" because it addresses their weakness?

    Is torquing circles less efficient than exerting power in a straight line, and so, since the larger diameter circle (from longer cranks) better approximates a straight line, it's more efficient?

    If there's more low-speed torque, what's the cause? Purely mechanical? Or is the rider able to exert more torque when his feet are further apart, perhaps due to certain core muscles (hip flexors?) becoming more accessible? Or are the legs able to provide a stronger counter force to each other?

  17. #17
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    The Benefits of Reducing Your Crank Length

  18. #18
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    Quote Originally Posted by Ryder1 View Post
    ... What do you think the benefits are? ...
    Honestly I have to say I believe it boils down to personal preference, just like handlebar width or grip diameter. In the end it really doesn't matter what crank length one prefers. One of my favorite aspects of cycling, road or mountain, is that each rider is able to create their own machine, set up exactly as they prefer, from HTA to suspension travel to gearing, including crank length.

    But to answer your question directly, my own preference is based on personal experience, not an understanding of biomechanics. I have a 36" inseam so long cranks work for me but I certainly wouldn't recommend them to anyone with short(er) legs. I do believe that crank length may be considered a bike fit issue albeit one based on personal preference.

    What I appreciate about the torque of long cranks is the way I'm able to mete out power. I live in Oregon near the western slopes of the Cascade Range where grades get wicked steep and our rainforested terrain gets slippery in the off season. The long levers allow me to keep traction in steep &/or slippery terrain because I'm better able to sense when I'm about to lose it. I believe longer cranks allow me to better feel my tires' connection with the terrain and then dole out power in a controlled manner that keeps my rear wheel from spinning out. My belief about the superiority of long cranks (for me, not necessarily for everyone) is that I'm often able to clean sections that others don't, and most times the others possess off-road riding skills at least equal to mine. When I clean a section others don't, crank length is one of the few bike setup differences I can point to.

    I grind up grades that I believe I would not clean on shorter cranks. (But I can't say for sure -- perhaps shorter cranks combined with a lower gear would get the job done as well.) If I stall out and stop on a steep hill, often I'm able to restart without putting a foot down and without spinning out, a situation I believe made more challenging by a shorter lever. As I mentioned previously, the longer lever allows me to mete out power in a very controlled way.

    I know that every time I get on a bike with 170-175mm cranks, I feel like I'm spinning a tricycle wheel. I admit that this may simply be because I've become so accustomed to longer cranks. My long legs are comfortable with them. This is probably the bottom line -- personal preference. I hope I didn't imply that I believe long cranks are for everyone.

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  19. #19
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    I fall into the longer 'cranks work for me' group. Maybe if I rode more rolling terrain the preference would be towards shorter cranks, spinning and rpm's. I run 180s on my ss.

  20. #20
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    I would like to second Sparticus.

    Anecdotally, as a 6'5" man that has ridden 165, 170, 175, and 180 cranks all for extended periods on the road, I can say there is a difference in comfort if anything else. I'm big, so for me anything less than 175mm feels awkward because my legs movement is more limited. I think I have 170mm on my track bike right now, and talk about a short pedal stroke. Yes, you can get used to it but why go through that? (I had to learn the hard way) I now have 180mm on the mtb, and 180 and 175 on my two road bikes. Going back and forth, I can feel the difference and 180 is more natural.
    Los Angelino looking to escape the clamor.

  21. #21
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    Man, you guys are tall!

    A while back I started to have discomfort in my hip flexor, at the same time I noticed in a riding photo that my knees seemed to come up very high in a seated pedal stroke. This was with my seat height optimized for leg extension at the bottom of the pedal stroke. At the time I was building a cross bike up and decided to do a professional fitting based on these two developments.

    I'm 5'10", but as it turns out have some abnormal leg proportions and ended up being fit with 165mm cranks to my surprise! They felt a bit spiny at first but instantly felt so much better at the top of the pedal stroke and took no time getting use to. The fitter and I also discussed my SS MTB's and he felt comfortable recommending I could go up to 170mm for that purpose.

    I changed both my SS trail bikes over from 175mm to 170mm, confirmed gearing with Sheldon Brown's gain ratio calculator, and have never felt better. I didn't notice ANY difference in climbing whatsoever, if anything I'm in a more powerful position for more of the pedal stroke than when my knee was getting too high with the longer cranks. As an added benefit, I get less pedal strike which comes in super handy for Central Texas.

    I think to say longer crank is better across the board, solely based on the concept of leverage, is making it way to one dimensional.
    Pedal through it!

  22. #22
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    Quote Originally Posted by Ryder1 View Post
    Or more precise application of torque at low speeds? Both? I imagine 130 cranks would be very clumsy for applying high torque at low-speed
    Quote Originally Posted by Sparticus View Post

    What I appreciate about the torque of long cranks is the way I'm able to mete out power. [...] The long levers allow me to keep traction in steep &/or slippery terrain because I'm better able to sense when I'm about to lose it. I believe longer cranks allow me to better feel my tires' connection with the terrain and then dole out power in a controlled manner that keeps my rear wheel from spinning out.
    I think you better expressed what I was getting at -- the increased precision (ie modulation or deftness) in delivering power, and it's effect on traction, enabling you to "sense when I'm about to lose it" - which is pretty useless in the cycling world, except for off-road climbing, and especially for low RPM, traction-challenged climbs. Whether seated or standing. I feel smaller cranks create more of an on/off power delivery, but others with superior neuromuscular skills (ie athletic) may not struggle with this as much.

    I've yet to use oval rings, but it sounds like they also create a more controlled power delivery, especially during low RPM climbs. Have you used an oval?

  23. #23
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    Quote Originally Posted by Hairnet View Post
    Crank length is not a problem for the most of the trails I have access to. Is Zinn the only maker of cranks over 180mm? I'm 6'5" and so far longer feels better.
    I thought there was someone else making longer cranks...Pro-something? When I last looked into it, the options weren't encouraging. Plus my trails are very rocky, and BB heights are only getting lower, so I abandoned the idea of ever exceeding 180. I actually sold one bike I loved (original Trance) b/c excessive pedal strikes. But 185 on a SS does sound intriguing to me, especially since SS is such that you can design some extra BB height into a bike (frame choice, fork choice, taller tires, 29s on 27.5+ frame).

  24. #24
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    Quote Originally Posted by Ryder1 View Post
    ...

    I've yet to use oval rings, but it sounds like they also create a more controlled power delivery, especially during low RPM climbs. Have you used an oval?
    I haven't tried an oval ring yet. I've heard nothing but good things.

    But I have some leftover Biopace rings LOL! Back in the day, Shimano seemed to put the bulges in exactly the wrong position on Biopace. The dead spot was through the mid-stroke. I rotated them by one bolt but back then cranks employed a 5 bolt spider so the ring couldn't be shifted exactly 90 degrees. I went back to round.

    Backing up to your previous thread, thanks for bringing up the application of power thing. Other than the comfort that my long legs appreciate about long cranks, accuracy of power delivery (for lack of a better description -- is that called torque?) is probably the greatest benefit to me.

    It's mighty muddy here in western Oregon right now. I need all the help I can get.
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  25. #25
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    6'5, long legs and run 180mm cranks with an oval ring.

    Love the setup and I think it's made my mtbing smoother/grippier/faster, but honestly don't notice much feel difference between that and my crossbike SS setup, which has 175mm cranks and a round ring. When I rode the oval ring for the first time it felt funny, now they both just feel like pedaling a bike....and I go back and forth every day and feel no difference.

    I will say though, the crossbike gives me IT band issues after a few hours on it, whereas I can go 10+ hours straight on my SS bike and have no knee/itband pain whatsoever. Could be a different fit factor thing though, haven't figured it out yet.

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