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  1. #1
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    New question here. New Guy intro + crank length question

    Howdy –

    I just wanted to say hello and introduce myself to the SS clan. I recently converted an old Stumpjumper to SS and discovered what you guys (and girls) already know to be pure, unadulterated fun on a bike. I’m hooked! Not only that, but seeing some of the pics of your blinglespeeds is making me drool and my wallet starting to squirm!

    I live and ride in the So. Cal. area and think I have met some of you (at least in passing….meaning: you passed me!) out on the trail. If I’m guessing correctly, that would be Poacher, Donkey and Hugh. Hopefully we’ll see each other out on the trails after the rain dries up a little…the conditions will be great.

    As a newbie to the SS thing, I’ve learned a lot from the FAQ’s and the postings. One topic I didn’t see too much info on was crank length. I’m 6’1” and right at about Clydesdale weight (200+ with my gear on) and was considering 180mm cranks. Anyone have an opinion on 175mm vs. 180mm? I know there should probably be more leverage with the longer cranks, but do you really feel a difference?

    Any info would be appreciated.

    Thanks,

    Dirk

  2. #2
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    Quote Originally Posted by DirkSSter
    Howdy –

    I just wanted to say hello and introduce myself to the SS clan. I recently converted an old Stumpjumper to SS and discovered what you guys (and girls) already know to be pure, unadulterated fun on a bike. I’m hooked! Not only that, but seeing some of the pics of your blinglespeeds is making me drool and my wallet starting to squirm!

    I live and ride in the So. Cal. area and think I have met some of you (at least in passing….meaning: you passed me!) out on the trail. If I’m guessing correctly, that would be Poacher, Donkey and Hugh. Hopefully we’ll see each other out on the trails after the rain dries up a little…the conditions will be great.

    As a newbie to the SS thing, I’ve learned a lot from the FAQ’s and the postings. One topic I didn’t see too much info on was crank length. I’m 6’1” and right at about Clydesdale weight (200+ with my gear on) and was considering 180mm cranks. Anyone have an opinion on 175mm vs. 180mm? I know there should probably be more leverage with the longer cranks, but do you really feel a difference?

    Any info would be appreciated.

    Thanks,

    Dirk
    I use 175's personally, and you and I are the exact same dimensions. I have some 180's as well, but I am just used to the 175's as they are also on two other bikes I own. I can definitely climb a bit better (and stay in the saddle a bit more) with the 180's, though. It's really a toss up for me as I don't think, for me at least, the slight added leverage makes a significant difference.

  3. #3
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    Quote Originally Posted by Justin Rempe
    I use 175's personally, and you and I are the exact same dimensions. I have some 180's as well, but I am just used to the 175's as they are also on two other bikes I own. I can definitely climb a bit better (and stay in the saddle a bit more) with the 180's, though. It's really a toss up for me as I don't think, for me at least, the slight added leverage makes a significant difference.
    I'm a little taller than you... Just over 6'4" and I use 180s. I'd use 185s if I could. It does take a little getting used to, but now any time I ride anything shorter, I feel like I'm riding a a toy bike.

    A lot of this is what you're used to.

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  4. #4
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    You'll be seeing me soon to then.

    I'm 6'6 and I run 180mm. Donkey runs 180mm too, I think.

    I'm sure the Oregon boys will chime in soon and encourage you to jump straight to their foot and a half long 200mm cranks... =)

    I'm really happy on my 180mm. I would consider 185mm but would never go higher than that.

  5. #5
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    I'm not entirely sure the 180's (and definitely not the 185's) would hold up under my cranking. My lower body is stronger than an ox (6'1" and 210, and I squat 500lbs/clean 240lbs)...so I'm sure the slight added flex of the longer arms would definitely cause me some problems.

  6. #6
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    I think there are pros and cons of both sizes, but personally I like the 180's. Shorter cranks are easier to spin faster. That's why you'll see 170mm cranks on most track bikes. If you were on a relatively flat course, the shorter cranks would probably be better. Besides giving you a little leverage up hills, the big diffrence that I noticed with the longer cranks is they help with instant acceleration. Going through intersections and going up over rock gardens is alot easier (just watch out for the bottom of the cranks!) witch I think compements the mechanical advantages of a singlespeed.

  7. #7
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    Crank length

    Welcome DirkSSter.

    Uh, did you say it's raining in SoCal? That's a physical impossibility, isn't it?

    I'm one of those long-cranked Orygunians that Padre warned you about. I ride bikes with cranks in the 195mm-202mm range (got four of 'em set up thisaway). I'm 6'3" with a 36" inseam if it matters.

    Long cranks improve leverage and torque. They reduce the ability to spin. They also increase the range of motion of your legs. Of course you're only talking about 5mm (between 175mm and 180mm) so that's not a lot, but even 5mm is enough to feel and enough to make a difference in torque and leverage.

    Above, Justin mentioned some worries about crank strength with regard to long cranks. In a dozen years of hard use I've encountered no equipment failure issues while riding really long cranks. Well designed equipment should be up to the task. Weigh a set of, say, 190mm Profile steel cranks sometime... I can just about promise you that nobody will be bending them anytime soon. And even if they could bend them, those particular cranks are guaranteed for life anyway.

    I guess I should mention that I did indeed rip a hub in half while using 202mm cranks once back in '93. It was a screw-on freewheel type hub; the portion with the freewheel threads sheared right off the spoke flange part. Tore the dang thing clean in half. So much for a demonstration of what extra torque can do, eh.

    If you decide to go to longer cranks, I have some recommendations for you:
    1. Don't decide you like them or don't like them until you've spent at least 30-40 hours riding them. It'll take that long for your legs to get used to spinning the larger circle. Muscles need to adapt. Personally, when I first tried really long cranks, I did not like them. (Now I love them.)
    2. Lower your saddle by the same measurement as the difference in length between your old, shorter cranks and your new, longer ones. You want your legs to extend the same amount that they used to.
    3. Lower your stem by the same amount.
    4. Move your saddle forward by the same amount. You'll want to maintain the same knee-over-pedal-spindle you used to have.
    5. Buy a longer stem by -- you guessed it -- the same amount. This will account for the shortened cockpit caused by moving your saddle forward.
    I've ridden with tall riders who prefer short cranks and short riders who prefer long cranks. Even though long cranks make sense for long legs, it still seems to boil down to a matter of individual preference.

    Good luck, and I hope you continue to enjoy singlespeeding.

    --Sparty
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    We get old because we quit riding.

  8. #8
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    Thanks for the tips...

    I appreciate the advice very much....especially Sparty's recommendations for modifying the cockpit set up, (something I didn't consider originally). Changing from 175mm to 180mm isn't something I'd do on my budget/converted SS...but it might come into play when I decide to build a new one from scratch.

    Until then, I'm just looking forward to getting out to ride so I can become stronger and smoke my "multi-geared" friends! (Is it wrong to think that way? )

    Cheers,

    D

  9. #9
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    www.cranklength.info

    Short version : cranks should be around 20% of your inseam length. Would a 4 yard tall giant be thinking between 175 and 180? No, more like between 360 and 400mm.
    How about a 3 foot chird? Those seem to do fine with cranks longer than that 20% even.
    Cranklengths, especially ones closer to the ideal take time to get used to, and are even very rare when you're an adult. Miguel Martinez is a tiny racer on 175mm's, imagine what you'd be running. Me, about 220mm then.
    Klok - XC - Skate - Ski

  10. #10
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    180's for me.

    I'm 6'3" and I'm riding a 22" surly. I like the extra torque and leverage I get with the 180 cranks. Sometimes I'll hit the pedals more on the rocks, but this is a fair tradeoff for me.
    Have fun SS'ing.
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  11. #11
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    Here's some useful info.....

    This is a decent discussion of crank length issues. I'm 6'4, 2much, and going from 180's to 200's on my SS was a revelation in carcass levitation-they've made a huge difference in my climbing. There is a period of adjustment for your bod, and they do pretty much change the whole setup of your bike.

    I got mine here. Good folks to deal with.

    Check out the science, and don't feel like you have to settle for what the industry is willing to make easily available.
    Last edited by quaffimodo; 10-22-2004 at 12:24 AM. Reason: Because keeping America safe by staying on the offensive is hard work.....

  12. #12
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    I have a somewhat on topic ?. One thing that has always bugged me when riding is that my left leg is definitely shorter than my right. So if my seat is adjusted perfectly for one leg its never right for the other. I originally thought I would use some sort of shim under my cleat but that proved to be dificult to execute cleanly. So now that ebay has made random crankarms much more available I am thinking about running two different sizes.

    Has anyone ever done this? I am trying to convince myself that it would work and spin smoothly but I'd like to hear everyones thoughts.

  13. #13
    Nat
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    Quote Originally Posted by lucifer
    I have a somewhat on topic ?. One thing that has always bugged me when riding is that my left leg is definitely shorter than my right. So if my seat is adjusted perfectly for one leg its never right for the other. I originally thought I would use some sort of shim under my cleat but that proved to be dificult to execute cleanly. So now that ebay has made random crankarms much more available I am thinking about running two different sizes.

    Has anyone ever done this? I am trying to convince myself that it would work and spin smoothly but I'd like to hear everyones thoughts.
    How much shorter is your left leg than your right?

    Different sized cranks means that only one leg will have proper extension. I'd build up the insole, shoe, or cleat instead.

    Oh, I just switched from 175mm to 180mm cranks and can tell a difference. Only 180's or longer for me from now on.

  14. #14
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    Quote Originally Posted by Nat
    How much shorter is your left leg than your right?

    Different sized cranks means that only one leg will have proper extension. I'd build up the insole, shoe, or cleat instead.

    Oh, I just switched from 175mm to 180mm cranks and can tell a difference. Only 180's or longer for me from now on.
    If I had to guess I'd say around 10mm or a little less than half an inch.
    Seems to me like both legs could be properly extended if you put the shorter crank with the shorter leg.

  15. #15
    Nat
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    Quote Originally Posted by lucifer
    If I had to guess I'd say around 10mm or a little less than half an inch.
    Seems to me like both legs could be properly extended if you put the shorter crank with the shorter leg.
    Yeah, maybe you're right. Let me know how it goes. Maybe try a chiropracter first. Hey, didn't we have this discussion a few weeks ago, or was that someone else?

  16. #16
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    Nope wasn't me.

    I'm gonna keep watching ebay for an appropriate crankarm.
    Unless someone has a red ano raceface turbine non drive side in 170 or a drive side 180 sitting around that they would care to donate....

  17. #17
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    Quote Originally Posted by lucifer
    Nope wasn't me.

    I'm gonna keep watching ebay for an appropriate crankarm.
    Unless someone has a red ano raceface turbine non drive side in 170 or a drive side 180 sitting around that they would care to donate....
    i hope you can excuse my ramblings below. this is a pretty interesting topic to me....

    be careful with the idea of using different length cranks.

    is your leg actually short or do you have scoliosis or some other reason that you leg appears to be shorter? for example, my right leg appears to be about 1/2" shorter, but it is actually my train wreck of lower back that is throwing things out of whack.

    if your legs are actually the same length and some other issue is causing them to appear different, then changing the cranks is definitely going to change the mechanical advantage that your muscles have. the result will be one leg working harder than the other and this may compound or aggravate the original cause of your problem.

    additionally, if one of your legs is actually shorter, you need to know if its the femur, the shin or both that are shorter and then exactly how much shorter. then you need to calculate how much shorter your cranks need to be in order to regain your lost mechanical advantage....hmmm, actually, in order to get the same mechanical advantage you would need a longer crank for the shorter leg. or does it depend on whether it is your femur or your lower leg is shorter. damnit. now i'm not sure anymore.

    i think you would really have to put a lot of effort into making the two different sized crank arm produce any positive result.

    the one thing i am pretty sure of is that i would go with a shoe insert before fiddling with different length cranks.

    i'll think about this a little more and maybe even do some 'back of the envelope' calculations if i'm feeling ambitious.
    To air is human, to dig is divine.

  18. #18
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    Another resource...

    Quote Originally Posted by DirkSSter

    Any info would be appreciated.

    Thanks,

    Dirk
    Check this guy out. I really respect his opinion and have found this site useful for all types of fit questions:

    http://www.peterwhitecycles.com/fitting.htm

    Late,
    James
    ---------------
    my bike sucks!

  19. #19
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    Quote Originally Posted by chuffer
    i hope you can excuse my ramblings below. this is a pretty interesting topic to me....

    be careful with the idea of using different length cranks.

    is your leg actually short or do you have scoliosis or some other reason that you leg appears to be shorter? for example, my right leg appears to be about 1/2" shorter, but it is actually my train wreck of lower back that is throwing things out of whack.

    if your legs are actually the same length and some other issue is causing them to appear different, then changing the cranks is definitely going to change the mechanical advantage that your muscles have. the result will be one leg working harder than the other and this may compound or aggravate the original cause of your problem.

    additionally, if one of your legs is actually shorter, you need to know if its the femur, the shin or both that are shorter and then exactly how much shorter. then you need to calculate how much shorter your cranks need to be in order to regain your lost mechanical advantage....hmmm, actually, in order to get the same mechanical advantage you would need a longer crank for the shorter leg. or does it depend on whether it is your femur or your lower leg is shorter. damnit. now i'm not sure anymore.

    i think you would really have to put a lot of effort into making the two different sized crank arm produce any positive result.

    the one thing i am pretty sure of is that i would go with a shoe insert before fiddling with different length cranks.

    i'll think about this a little more and maybe even do some 'back of the envelope' calculations if i'm feeling ambitious.
    Those are very good things to consider.
    I suppose I will need to get good measurements and maybe consult a sports med specialist or something.

  20. #20
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    Quote Originally Posted by chuffer
    i hope you can excuse my ramblings below. this is a pretty interesting topic to me....

    be careful with the idea of using different length cranks.

    is your leg actually short or do you have scoliosis or some other reason that you leg appears to be shorter? for example, my right leg appears to be about 1/2" shorter, but it is actually my train wreck of lower back that is throwing things out of whack.

    if your legs are actually the same length and some other issue is causing them to appear different, then changing the cranks is definitely going to change the mechanical advantage that your muscles have. the result will be one leg working harder than the other and this may compound or aggravate the original cause of your problem.

    additionally, if one of your legs is actually shorter, you need to know if its the femur, the shin or both that are shorter and then exactly how much shorter. then you need to calculate how much shorter your cranks need to be in order to regain your lost mechanical advantage....hmmm, actually, in order to get the same mechanical advantage you would need a longer crank for the shorter leg. or does it depend on whether it is your femur or your lower leg is shorter. damnit. now i'm not sure anymore.

    i think you would really have to put a lot of effort into making the two different sized crank arm produce any positive result.

    the one thing i am pretty sure of is that i would go with a shoe insert before fiddling with different length cranks.

    i'll think about this a little more and maybe even do some 'back of the envelope' calculations if i'm feeling ambitious.

    Well, a shorter crank on one side will be at a mechanical disadvantage compared to the longer side for sure. It will be harder to pedal the shorter side, and cause some uneven wear on the BB bearings (I would think anyway). Basically, you'd be able to pedal the longer side easier and faster, but you would unevenly distort muscle mass (more mass/strength) on the shorter side, which will cause numerous lower back and hip problems. Hell, sounds like bad news to try this to me...

  21. #21
    Nat
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    Quote Originally Posted by lucifer
    Those are very good things to consider.
    I suppose I will need to get good measurements and maybe consult a sports med specialist or something.
    I'm thinking 99 out of 100 sports med specialists will recommend an orthotic built up on one side. Why? Because that's textbook treatment for a leg length discrepancy (plus you can bill for it ). Only a few sports medicine specialists have extensive and current cycling biomechanics knowledge, and of those, only a few might have the answer to your question about different crank lengths. Even then, it'd probably be an educated guess rather than anything based on controlled research.

    If you're serious about it, then you may want to book a flight to Boulder and get an appointment with Andy Pruitt.

    http://www.bch.org/sportsmedicine/science.cfm

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