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Thread: Long Cranks

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    Long Cranks

    Anyone running long cranks, 180s, 190s? What are your ride impressions? Considering Zinn 195s, maybe Surly 180s. I feel like my 175s are too small. 6'5" on a '10 Sultan running XX.

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    Seems like an on-going debate whether us taller riders really benefit from using longer cranks.
    My bikes are pretty much stock, so have 175's on Stumpjumper FS and 180's on Stumpjumper HT.....As some other's have mentioned, you just get used to what size you ride.
    About the only thing I'm sure of is that your possibility of pedal-strikes increases with longer lengths, especially on a FS bike.

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    200mm and 205mm on my bikes. If you are tall it only makes sense. After riding really long cranks for 2 years, I get on a bike with 180mm and it feels like a kids bike.
    Last edited by phoeve; 02-20-2011 at 10:41 AM.

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    I run 180s on my mountain bikes, 170mm on my fixed gear, and looking at running 180mm SRAM cranks on my upcoming cross/touring bike build.

    Do it! You can get Truvativ Stylos for cheap to see if you like the longer crankarms.

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    I tried 180's on my bike and I love em. Thinkin' about trying some longer ones.
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    Surly Mr. Whirly crank arms are available in 185's as well, and at a reasonable price.

    Personally, I'd imagine that there is a rule of diminishing return with really big crank arms, say >190mm. You will need to have a high bb to accomodate the arms, or pedal/crank strikes will happen all the time. But, the high bb may throw off bike handling/geometry, and any technical riding will suffer IMO. 180 is the biggest I have gone, but already bash my stuff all the time in the local rocks.

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    I appreciate everyone's input. After a bit of fit theory and crank research, number crunching and biasing for ride type, seat angle; rail position, shoe size, cleat position, XX gearing, and bottom bracket height, I've determined that I need 200mm cranks. The most compelling literature I found was written by Zinn. http://zinncycles.com/Zinn/index.php/archives/1399

    Also, as some have pointed out, we are guilty of becoming accustomed to what we ride and changing will take a little getting used to. Therefore, it may be a little while until I get my bike dialed and I adjust to the changes; I'll try to provide an objective ride report when I can.

    Ride On!

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    Quote Originally Posted by burgundy snake
    I appreciate everyone's input. After a bit of fit theory and crank research, number crunching and biasing for ride type, seat angle; rail position, shoe size, cleat position, XX gearing, and bottom bracket height, I've determined that I need 200mm cranks. The most compelling literature I found was written by Zinn. http://zinncycles.com/Zinn/index.php/archives/1399

    Also, as some have pointed out, we are guilty of becoming accustomed to what we ride and changing will take a little getting used to. Therefore, it may be a little while until I get my bike dialed and I adjust to the changes; I'll try to provide an objective ride report when I can.

    Ride On!
    From the above article:
    3. A stock mass-produced mountain bike will probably not have a high enough bottom bracket to ride on technical trails with a crank any longer than 175mm or perhaps 180mm.

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    Quote Originally Posted by Jeff in Bend
    From the above article:
    3. A stock mass-produced mountain bike will probably not have a high enough bottom bracket to ride on technical trails with a crank any longer than 175mm or perhaps 180mm.
    True. My bike came with 175s and I swapped on 180's. Doesn't sound like much, but I definitely have more strikes.
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    Quote Originally Posted by NYrr496
    True. My bike came with 175s and I swapped on 180's. Doesn't sound like much, but I definitely have more strikes.
    I just just did the same but haven't been able to ride with them except around the hood. Other than the strikes what's been your experience?

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    That is dissapointing to hear. NY, what is your BB height? I was hoping to throw a longer fork on to alieviate the problem. Besides I like a HT angle a bit slacker.

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    Specialized says the BB height is 328 mm. It's a full suspension bike, so it changes constantly. I used to run Crank Bros Mallets on the bike, once I went to the 180's, and started hitting the ground, I switched to Eggbeaters and changed my riding style a little. I really hit the ground very little any more. Mostly in turns if at all any more.
    I did notice an increase in mechanical advantage. I climb a little easier. I'll not be going any shorter ever again. I have to check the BB height on my Kona HT. If it's a little higher, I may try some 185's.
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    x2 on pedal selection dictating the frequency of pedal strikes... but not crank arm strikes. I ran platforms and Mallets for a while, but not anymore.

    Tire selection can also change your bb height substantially as well. I run some large volume tires (2.4 Purgatories and Ardents among them), that can easily raise your bb height by 5mm or more to accommodate longer cranks.

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    Quote Originally Posted by Pitch
    x2 on pedal selection dictating the frequency of pedal strikes... but not crank arm strikes. I ran platforms and Mallets for a while, but not anymore.

    Tire selection can also change your bb height substantially as well. I run some large volume tires (2.4 Purgatories and Ardents among them), that can easily raise your bb height by 5mm or more to accommodate longer cranks.
    That's a great point. I just swapped the rims on my bike to Salsa Gordos and they changed the profile of the tire significantly. The bike is absolutely a little higher. I just had my first ride in over a month today. Too much snow. I didn't realize it at the time, but I had zero strikes.
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    Quote Originally Posted by burgundy snake
    I appreciate everyone's input. After a bit of fit theory and crank research, number crunching and biasing for ride type, seat angle; rail position, shoe size, cleat position, XX gearing, and bottom bracket height, I've determined that I need 200mm cranks. The most compelling literature I found was written by Zinn. http://zinncycles.com/Zinn/index.php/archives/1399

    Also, as some have pointed out, we are guilty of becoming accustomed to what we ride and changing will take a little getting used to. Therefore, it may be a little while until I get my bike dialed and I adjust to the changes; I'll try to provide an objective ride report when I can.

    Ride On!
    Zinn has sold you a bill of goods and he makes a good living doing it. If you consider his "literature" compelling, why haven't you looked for even the most rudimentary data that suggests it is true? Zinn won't offer it no matter how badly he wants to. Other than formulas that have no data behind them, what has led you to determine a length of 200mm?

    I agree with Pitch who said there is "a rule of diminishing returns with really big crank arms". Testing has shown "really big" to be about 150mm surprisingly. We all get long enough crank arms stock on every bike. There's a lot of confirmation bias regarding long crank arms since there's so many claims that proportional cranks are needed. You won't find a single objective test that shows any value to long cranks though.

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    B_S - I'm taller than you also on a Sultan and I run 180mm Shimano XT cranks. They do feel better than the 175s I had on my old bike. I am very tempted to try the 185 Mr Whirlys as I think I could just about get away with that on a stock frame - and my other bikes wouldn't feel too odd when swapping back to them.

    You'd be dropping quite a lot of cash on some 200mm cranks, then buying new long forks - that would be a lot of money for an experiment that would probably not work. You really need a custom frame for cranks that long. I would suggest a 185 Mr Whirly crank set first and see whether 10mm makes a big enough difference for you - it probably will. Less risk as you'll always be able to sell them on.

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    Quote Originally Posted by craigsj
    Zinn has sold you a bill of goods and he makes a good living doing it. If you consider his "literature" compelling, why haven't you looked for even the most rudimentary data that suggests it is true? Zinn won't offer it no matter how badly he wants to. Other than formulas that have no data behind them, what has led you to determine a length of 200mm?

    I agree with Pitch who said there is "a rule of diminishing returns with really big crank arms". Testing has shown "really big" to be about 150mm surprisingly. We all get long enough crank arms stock on every bike. There's a lot of confirmation bias regarding long crank arms since there's so many claims that proportional cranks are needed. You won't find a single objective test that shows any value to long cranks though.
    Can you provide where we could find these test that say 150mm crank arms are really big?
    I would like to read them. I don't think I would ever go to what Zinn recommends for my leg length because I don't want a BB that's 15" high. I'm going to try some 180's this season and see if I feel an advantage, but I'm keeping my 175's just in case. I have a 38" inseam.

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    Quote Originally Posted by Jeff in Bend
    Can you provide where we could find these test that say 150mm crank arms are really big?
    I would like to read them. I don't think I would ever go to what Zinn recommends for my leg length because I don't want a BB that's 15" high. I'm going to try some 180's this season and see if I feel an advantage, but I'm keeping my 175's just in case. I have a 38" inseam.
    Here is something I've linked to a number of times: Martin crank length presentation. This is a slide presentation that summarizes some studies on crank length.

    Regarding "really big" I obviously took liberties with that term. Pitch said there must be a point of diminishing returns and Martin has shown that for virtually all adult riders, "long enough" occurs at least by 150mm. He personally believes that number is due to his testing methodology and thinks it could be lower still. Finding his personal comments on the matter takes some digging on the slowtwitch forums.

    The TLDR version, crank length doesn't matter. Choose it for whatever reasons you have, ground clearance being a really good one, but don't choose it believing your performance will be better as Zinn says. It won't be.

    The beauty of crank length making no difference is it allows people's biases to be sustained. No matter what you personally believe, your own testing will confirm it. That seems to carry great weight with cyclists.

    Regarding your reluctance to consider extra long cranks with a higher bottom bracket, I think that's wise. A very long crank will also put the pedal further forward meaning that you will be either more upright or further forward on the seat. It's unlikely that would work well with overall fit. If I were to do a custom frame to accommodate and unusual crank, I'd go extra short. I don't think it's worth the effort though.

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    Quote Originally Posted by craigsj
    Here is something I've linked to a number of times: Martin crank length presentation. This is a slide presentation that summarizes some studies on crank length.
    That presentation wasn't put together very well, but I got the jist of it. What I've seemed to notice that all the data gets measured for peak efficiency or output but I've not seen any tests were someone is measureing power at real slow cadences were no one reaches max cadence output or pedal speed. Like grinding up a steep hill in your lowest gear.

    This is what seems logical to me. If I have a 38" inseam compared to someone with a 32" I would use less% of my total range of motion if we use the same crank length. If we both used the same % of our range of motion my cranks would be longer. A longer crank would give more leverage than a shorter crank and more tourqe to the rear wheel when in the same gear.

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    Quote Originally Posted by Jeff in Bend
    That presentation wasn't put together very well, but I got the jist of it. What I've seemed to notice that all the data gets measured for peak efficiency or output but I've not seen any tests were someone is measureing power at real slow cadences were no one reaches max cadence output or pedal speed. Like grinding up a steep hill in your lowest gear.
    One of the studies quoted looked at metabolic costs at submaximal loads (30, 60, and 90 percent). The test methodogy included allowing cyclists to pick their preferred cadence to avoid biasing against short cranks (a failure in some testing). That means, of course, that there's an assumption that you will have the right gear for the task, not one that doesn't allow for the best cadence. I'm not sure what it says about running out of low gears, but what it says to me is that I shouldn't let that happen. I know that shorter cranks need lower gearing so I provide it.

    Martin is mostly concerned with road racing and sprinting so he studies peak power, but most cyclists who talk about long cranks and leverage are talking about peak power too. It doesn't seem important what crank you choose when you're just cruising along.

    Quote Originally Posted by Jeff in Bend
    This is what seems logical to me. If I have a 38" inseam compared to someone with a 32" I would use less% of my total range of motion if we use the same crank length. If we both used the same % of our range of motion my cranks would be longer. A longer crank would give more leverage than a shorter crank and more tourqe to the rear wheel when in the same gear.
    Regarding leverage, read what Sheldon Brown says. I've tried to explain this a number of times here on MTBR but it's never received well. Sheldon Brown is more respected. To summarize, longer cranks do not provide better leverage or more torque in the same gear, what they do is change what that "gear" is.

    What really matters is how fast your feet move around the circle. When you equalize foot speed, maximum power equalizes as well. The reason a longer crank puts down more power for a given gear at a given cadence is that the legs produce more because the feet travel further (power is force times distance over time). What's important to understand is that legs produce power, not cranks. A longer crank can't make more power because cranks don't make any.

    Regarding your other point, the biomechanical aspects are what's really interesting and where you'd think the real differences in crank length would be. The Martin study showed, though, that it barely matters at all. To quote from his slide, "170mm cranks will compromise power of the tallest and shortest riders by at most 0.5%".

    Martin, in discussing his results on the slowtwitch forums, pointed out that his tests did reveal an optimum crank length computable from rider dimensions (and even gave a formula), but the thing is that ignoring it comes at no cost. It's not that there isn't a best answer, it's just that it doesn't matter. Formulas like Zinn's are merely extrapolated from what has been traditionally done, there's absolutely no reason to believe any of it regardless of how reasonable the explanations seem to be. Zinn has tried to perform testing to verify his claims but his results have never been published because, and this comes from Zinn himself, his data wouldn't pass peer review and contradicted his own advice. In other words, he knows it's wrong but he makes money selling it.

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    Quote Originally Posted by craigsj
    One of the studies quoted looked at metabolic costs at submaximal loads (30, 60, and 90 percent). The test methodogy included allowing cyclists to pick their preferred cadence to avoid biasing against short cranks (a failure in some testing). That means, of course, that there's an assumption that you will have the right gear for the task, not one that doesn't allow for the best cadence. I'm not sure what it says about running out of low gears, but what it says to me is that I shouldn't let that happen. I know that shorter cranks need lower gearing so I provide it.

    Martin is mostly concerned with road racing and sprinting so he studies peak power, but most cyclists who talk about long cranks and leverage are talking about peak power too. It doesn't seem important what crank you choose when you're just cruising along.


    Regarding leverage, read what Sheldon Brown says. I've tried to explain this a number of times here on MTBR but it's never received well. Sheldon Brown is more respected. To summarize, longer cranks do not provide better leverage or more torque in the same gear, what they do is change what that "gear" is.

    What really matters is how fast your feet move around the circle. When you equalize foot speed, maximum power equalizes as well. The reason a longer crank puts down more power for a given gear at a given cadence is that the legs produce more because the feet travel further (power is force times distance over time). What's important to understand is that legs produce power, not cranks. A longer crank can't make more power because cranks don't make any.

    Regarding your other point, the biomechanical aspects are what's really interesting and where you'd think the real differences in crank length would be. The Martin study showed, though, that it barely matters at all. To quote from his slide, "170mm cranks will compromise power of the tallest and shortest riders by at most 0.5%".

    Martin, in discussing his results on the slowtwitch forums, pointed out that his tests did reveal an optimum crank length computable from rider dimensions (and even gave a formula), but the thing is that ignoring it comes at no cost. It's not that there isn't a best answer, it's just that it doesn't matter. Formulas like Zinn's are merely extrapolated from what has been traditionally done, there's absolutely no reason to believe any of it regardless of how reasonable the explanations seem to be. Zinn has tried to perform testing to verify his claims but his results have never been published because, and this comes from Zinn himself, his data wouldn't pass peer review and contradicted his own advice. In other words, he knows it's wrong but he makes money selling it.
    Thanks for your input and links. So from what I gathered crank length is just another componet to gearing, longer cranks give you a lower overall gear ratio assuming everthing else stays the same, which in return would reduce top end speed due to the fact that you can't turn as many rpm's.

    The other things I'm interested in finding out is how the 180's are going to effect my descending with a longer stance, cornering with outside foot down, and having my pedaling seat position lower. These areas may be advantges to longer cranks if you have the range of motion to run them, we shall see.

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    Quote Originally Posted by Jeff in Bend
    Thanks for your input and links. So from what I gathered crank length is just another componet to gearing, longer cranks give you a lower overall gear ratio assuming everthing else stays the same, which in return would reduce top end speed due to the fact that you can't turn as many rpm's.
    Yes on all of that.

    Quote Originally Posted by Jeff in Bend
    The other things I'm interested in finding out is how the 180's are going to effect my descending with a longer stance, cornering with outside foot down, and having my pedaling seat position lower. These areas may be advantges to longer cranks if you have the range of motion to run them, we shall see.
    Those would be reasons you might like a longer crank but they depend on the frame too. I feel crank length should be chosen to suit frame and fit. It wouldn't make sense to have a custom frame made to enable abnormally long cranks IMO.

    The biggest thing I notice when switching crank lengths is the change in feel from seat height. I don't notice it in a trainer but on the road/trail so it's clearly a change in handling. The other aspects you mentioned I can't say that I notice. I've run 180mm on a road bike but 175 is the longest I've gone on MTB. I've gone as short as 165mm, shorter gets hard to find. My current bike is 165mm and I wished I'd gone shorter for the ground clearance.

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    Ground clearance? Not to sound like an elitist but once you get used to riding longer cranks, you learn where they are and how to backpedal to clear obstacles. 5mm is not much to suffer for ground clearance, lower profile pedals will get you back that 5mm. I had issues with pedal strikes when first running a 90s era rigid XC bike with a low bottom bracket and 180mm cranks on rocky, rooty east coast trails but once I learned where the pedals where and how to look out for obstacles it was no longer an issue. And frames being designed around a certain sized crank? Really? Your saddle stays in the same place, front to rear, and slightly lower, your pedals move forward a hair but not enough to affect frame geometry. Granted some frames may not have clearance for 180s, something to consider before investment . . .

    I guess people can run all sorts of calculations on whether long cranks work better or not but real world experience will tell you whether they are right for you or not. I've got a history of knee problems and I feel like the larger cranks require less flexion of my knee to complete the circle; that being said you will need to practice high-rpm spinning to feel comfortable on larger cranks. Longer cranks will tire you out more since the circumference of the pedal axis for each revolution is much longer. The torque advantage is immediate, your force output is the same and you have lengthened your torque arm; this makes it easier to strip rear hubs and break chains, not always a good thing.

    If you're in doubt, grab some used 180s and give them a whirl, it gets much harder to find longer cranks than that without going custom or using obscenely heavy (and strong) BMX cranks. My 170s on my fixed gear work well but they feel like I'm tiptoeing since the circles are so small relative to my size 14 feet.

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    Quote Originally Posted by GTscoob
    Ground clearance? Not to sound like an elitist but once you get used to riding longer cranks, you learn where they are and how to backpedal to clear obstacles.
    Wow, wish I'd thought of that! What makes you believe I don't know how to pedal, that I don't have "real world experience", that's I'm not using a good pedal already, etc.? It's not 5mm either. I already reduced my crank length, I simply said I wished I'd gone further. I have a low bottom bracket.

    I'll add further that a shorter crank creates no disadvantage so there's no reason to put up with poor crank clearance. The shorter crank also makes it easier to keep your weight back on the bike. That's useful for big wheeled bikes with longish chainstays. Meanwhile there's no argument whatsoever for long cranks on my bike.

    Quote Originally Posted by GTscoob
    I guess people can run all sorts of calculations on whether long cranks work better or not but real world experience will tell you whether they are right for you or not. I've got a history of knee problems and I feel like the larger cranks require less flexion of my knee to complete the circle; that being said you will need to practice high-rpm spinning to feel comfortable on larger cranks. Longer cranks will tire you out more since the circumference of the pedal axis for each revolution is much longer. The torque advantage is immediate, your force output is the same and you have lengthened your torque arm; this makes it easier to strip rear hubs and break chains, not always a good thing.
    You are wrong on all of this. I'd say you need to run some more "calculations" and lay off the "real world experience".

    Quote Originally Posted by GTscoob
    If you're in doubt, grab some used 180s and give them a whirl, it gets much harder to find longer cranks than that without going custom or using obscenely heavy (and strong) BMX cranks. My 170s on my fixed gear work well but they feel like I'm tiptoeing since the circles are so small relative to my size 14 feet.
    You just need to get used to riding larger shoes.

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    With big tires you can pick up some decent "crank clearance". I read all the science on the long crank debate before I went to 200mm's. The proof is in practical experience. I am completely sold. My cycling inseam is 102cm, YMMV. If you're tall and ever in the Atlanta area look me up and you can try mine - then you'll know.

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