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  1. #1
    Fred E Fenders fthomas's Avatar
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    Check Your Crank Length

    Has anyone experimented with changing your crank lengths. I was asked some interesting questions at the LBS this past weekend and decided to get some better answers. Most manufacturers just put the "standard" length on, whatever that is.

    Here is a link to an interesting article:

    Check Your Cranks
    F Thomas

    "Life is like riding a bicycle. To keep your balance, you must keep moving."
    Albert Einstein (1879-1955)

  2. #2
    Fred E Fenders fthomas's Avatar
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    Here is another site that I found:

    Bicycle Crank Length

    I think that I am going to go with a shorter crank on my touring bike.

    Any thoughts or experience?
    F Thomas

    "Life is like riding a bicycle. To keep your balance, you must keep moving."
    Albert Einstein (1879-1955)

  3. #3
    His Brain is Gone! Tom Bombadil's Avatar
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    We've had several discussions on this topic over the past year or so. I've seen some going in the past week.

    I currently have 170mm on three bikes, 165 on a fourth, and 155 on my recumbent.

    I think my favorite lengths are 165 on an upright bike and 155-160 on bents, but am not certain yet.

    Here's a crank arm length calculator. It tends to yield results that seem too short for most people.

    http://www.machinehead-software.co.u...alculator.html
    Last edited by Tom Bombadil; 06-25-08 at 12:11 AM.
    "Too often I would hear men boast of the miles covered that day, rarely of what they had seen." Louis L'Amour

    There are two types of road bikers: bikers who are faster than me, and me. Bruce Cameron - Denver Post

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    Senior Member late's Avatar
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    I use 167.5

    Works for me.
    We are as gods, we might as well get good at it.
    Stewart Brand

  5. #5
    His Brain is Gone! Tom Bombadil's Avatar
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    Bike companies lilke to put 175's on most bikes, except for their smallest bikes which get 170's.

    Personally, I think a lot of people use crank arms that are too long, and think they need them long to generate more power. Lab tests indicate that few riders actually generate more power with long cranks. In fact, some recent tests really surprised some racers when they saw that their maximum power curve was generated when they used 150mm cranks.
    "Too often I would hear men boast of the miles covered that day, rarely of what they had seen." Louis L'Amour

    There are two types of road bikers: bikers who are faster than me, and me. Bruce Cameron - Denver Post

  6. #6
    His Brain is Gone! Tom Bombadil's Avatar
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    I remember reading some material from Sheldon Brown when he experimented with shorter crank arms. He was surprised to find them more efficient than the longer cranks he had been using for many years.

    This article doesn't contain those particular statements, but it does capture the gist of his findings:
    http://www.sheldonbrown.com/cranks.html
    "Too often I would hear men boast of the miles covered that day, rarely of what they had seen." Louis L'Amour

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  7. #7
    Small Member maddmaxx's Avatar
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    Over the last couple of years I have changed down to the shortest length (still 170) that the cranks I use come in. I have no hard data, but my impression is positive, especially on a roadbike with a steady spin.

  8. #8
    Senior Member bobbycorno's Avatar
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    Quote Originally Posted by fthomas View Post
    Here is another site that I found:

    Bicycle Crank Length

    I think that I am going to go with a shorter crank on my touring bike.

    Any thoughts or experience?
    This appears to be the same formula that Lennard Zinn (framebuilder, VeloNews tech wizard, and all around tall guy) espouses. Since I have a 36" inseam, this would put me on 197.5's (yes, one NINETY seven). Considering that this isn't exactly a common size, and considering the knee problems I've experienced when trying 180's, I've stuck with 175's. They work fine, and I can turn 'em at 100+ rpms all day, no prob.

    Scott P
    Bend, OR

  9. #9
    Senior Member Fredmertz51's Avatar
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    29" inseam, 175mm cranks work for me.
    Just because I don't care doesn't mean I don't understand.

  10. #10
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    I've got a 35.5" inseam and ride a 61cm frame. It has 175's on it for the last 12k miles or so, but I'm going to experiment with some 172.5's that I recently bought to see how it works with my knee. (due to major surgery followed with staph infection many years ago I can't bend that knee much past 90*)

  11. #11
    3speed CitiZen's Avatar
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    We ladies out here are disappointed in the responses, considering the title of this thread! Phooey!

  12. #12
    Senior Member Wildwood's Avatar
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    Quote Originally Posted by CitiZen View Post
    We ladies out here are disappointed in the responses, considering the title of this thread! Phooey!
    Shucks, my 175 crank is only approx 6.9". Boo - Hoo
    Remember this is the 55+ Forum, so it's not about what you got but more about how long you can cycle.

  13. #13
    His Brain is Gone! Tom Bombadil's Avatar
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    We could start a thread about shoe size.
    "Too often I would hear men boast of the miles covered that day, rarely of what they had seen." Louis L'Amour

    There are two types of road bikers: bikers who are faster than me, and me. Bruce Cameron - Denver Post

  14. #14
    Fred E Fenders fthomas's Avatar
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    Why oh why has it degenerated to this?
    F Thomas

    "Life is like riding a bicycle. To keep your balance, you must keep moving."
    Albert Einstein (1879-1955)

  15. #15
    His Brain is Gone! Tom Bombadil's Avatar
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    It hasn't really degenerated very far yet.
    "Too often I would hear men boast of the miles covered that day, rarely of what they had seen." Louis L'Amour

    There are two types of road bikers: bikers who are faster than me, and me. Bruce Cameron - Denver Post

  16. #16
    Senior Member Bill Kapaun's Avatar
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    I'm the instigator of one of the crank length threads that resurfaced recently when I got an even shorter set of cranks, 175>170>160mm.
    Are Your Cranks Too Long?

    You might peruse the initial post and then skip to the end.
    In a nutshell- I'm 6" with about a 31" inseam, bad R, knee and 60 years old. Let's say my L. knee is "used".
    After going to 170's, there was GREAT improvement in speed & stamina. I came to the conclusion, that my bad knee didn't have enough range in motion to handle 175's. I was "sapping energy", carrying my R. knee "over the top".
    I was looking for 165's to take the experiment further, but didn't get there because of budget considerations.
    A couple weeks back, I ran across these on a different BF forum and though Why Not? If they didn't work, I wasn't out much $.
    http://www.nashbar.com/profile.cfm?c...20ATB%20Cranks

    My cadence increased approx. 10 more RPM, but my "apparent" gearing has changed very noticeably.
    I ride flat pavement on my "commuterized" 86 Rockhopper. When "cruising, I'm on the middle (38T) ring and using the 15 or 16T cog in calm conditions. I currently have a custom cassette with 13-14-15-16-17-19-21-24 cogs. I now wish I had a 12T top cog, so I could add an 18T for a bit more flexibility for head winds.
    My conditioning isn't really up to snuff though, so in a couple weeks I may be able to turn one gear higher?
    I have ALL those high gears on the big ring I can't use!
    I think 165's would probably work best for me.

    Anyway, if you have a square taper BB, there is a cheap method to find out what 160's will do. Be prepared for a VERY different sense of gearing though.

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