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  1. #1
    Triathlon in my future??? flip18436572's Avatar
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    Can I ask a Cranky question?

    What is the difference in crank length?

    What should I use and how should I know?

    I am 6' 3", but have a 33" inseam. I am using the stock cranks that came on my Jamis, but I am thinking of changes to make to the bike for next year and putting things on a Christmas list for the family. I haven't looked into pricing, so this might not even matter, but I am interested in finding out.

    THANKS!!!!!
    2007 Jamis Ventura Comp
    2006 Jamis Explorer 2.0
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    Swim, Bike, Run and sounds like fun

  2. #2
    Banned. Mr. Beanz's Avatar
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    I have 175 on my Lemond and 172.5 on my Cannondale. I don't notice a darn difference. Some say longer cranks allow a rider to apply more torque. SHorter carnks for spinning and long cranks for hammering. Some say longer cranks for climbing. I don't feel a thang!

    Look at the thread I post a few days ago "anybody buy from these guys". Ther is a link to some inexpensive cranks at an online ebay store. Ultegr triple for $149 including the bottom bracket.

    I went of the 10 speed setup, works fine with 9 speed drivetrain. I like the 10 speed acuse it is the new outboard bearing design. Much stiffer and durable. Old style is the bearing in the cartridge sytle. More toward the center of the BB allowing more flex and chance of damage/loosening..
    Usual online price is $250 without the BB (which is usuall about $50 more)

  3. #3
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    one consideration... when pedaling thru a turn and 'leaning into a turn' with the inside pedal @ 6 o'lcock, the longer cranks reduce the amount you can "lean into" the turn. you are more apt to 'catch the pedal' on the road. some may not consider the small increase in length significant, but it is simple geometry... it can make for a nasty spill....

    ....... did that babble make sense???
    You're only given a little spark of madness. You mustn't lose it. - Robin Williams

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    My Rides: '06 Giant OCR Limited & '95 GT OUTPOST

  4. #4
    Banned. Mr. Beanz's Avatar
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    Quote Originally Posted by Bone Head View Post
    one consideration... when pedaling thru a turn and 'leaning into a turn' with the inside pedal @ 6 o'lcock, the longer cranks reduce the amount you can "lean into" the turn. you are more apt to 'catch the pedal' on the road. some may not consider the small increase in length significant, but it is simple geometry... it can make for a nasty spill....

    ....... did that babble make sense???
    No! Depending on a .009 of an inch to make that much of a difference? A smart rider knows when to pedal and when not to pedal! I've smoked too many riders down mtn switchbacks. 30-40 mph switchbacks and descents for 20-30 miles and "Never" do I pedal through a turn! Knowing how to take the turn is way more important than where your pedal is at on the downside.

    Also on flat turns (crit race types), you hesitate with the pedals at the lowest point of the turn. You don't risk pedaling hoping .009 will save you!

    Ever watch TDF videos of the timetrials? Ever see the riders stop the pedals while taking sharp turns? Yes, then they continue after the sharpest point. Same with driving, you don't accellerate into a turn.

    BTW, have you ever read or seen diagrams on the most effective way to take turns? By taking the apex? If you learn how to porperly take turns, you will improve your turn speed and efficiency and NEVER hit the pedals!
    Last edited by Mr. Beanz; 11-02-08 at 06:08 PM.

  5. #5
    Triathlon in my future??? flip18436572's Avatar
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    So the length of the crank really doesn't depend upon the rider's inseam length at all, like I thought it would. I was thinking longer cranks for longer legs.
    2007 Jamis Ventura Comp
    2006 Jamis Explorer 2.0
    2000 Specialized Hardrock (bought used)
    Swim, Bike, Run and sounds like fun

  6. #6
    Senior Member dbikingman's Avatar
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    Quote Originally Posted by flip18436572 View Post
    So the length of the crank really doesn't depend upon the rider's inseam length at all, like I thought it would. I was thinking longer cranks for longer legs.
    What I have read is most manufacturers use longer cranks on the larger frame sizes. So I guess they do figure taller frame, longer inseam, longer crank.

  7. #7
    Senior Member Wogster's Avatar
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    Quote Originally Posted by Mr. Beanz View Post
    No! Depending on a .009 of an inch to make that much of a difference? A smart rider knows when to pedal and when not to pedal! I've smoked too many riders down mtn switchbacks. 30-40 mph switchbacks and descents for 20-30 miles and "Never" do I pedal through a turn! Knowing how to take the turn is way more important than where your pedal is at on the downside.

    Also on flat turns (crit race types), you hesitate with the pedals at the lowest point of the turn. You don't risk pedaling hoping .009 will save you!

    Ever watch TDF videos of the timetrials? Ever see the riders stop the pedals while taking sharp turns? Yes, then they continue after the sharpest point. Same with driving, you don't accellerate into a turn.

    BTW, have you ever read or seen diagrams on the most effective way to take turns? By taking the apex? If you learn how to porperly take turns, you will improve your turn speed and efficiency and NEVER hit the pedals!
    Tthe difference in crank lengths is often 2.5mm, which is .098" not .009", still, mountain bikes tend to have longer cranks (175mm vs 172.5mm for road bikes), and the training for starting mountain bikers, is to hold the pedals at 9 o'clock and 3 o'clock when going around curves or between things that can catch a pedal. However your unlikely to see a curve on a normal road that is sharp enough to require enough lean to catch a pedal.

  8. #8
    Banned. Mr. Beanz's Avatar
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    Oops, that's right, got my decimal mixed up!...almost 1/10 of an inch!

  9. #9
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    The 175 mm crank length is in general fine for most people. While what one poster said about the spinning and torque is correct, it's really only a real consideration for more extremes of height for the rider from what I understand.

    http://www.nettally.com/palmk/crwives.html

    That's a site I found with some theoretical information about crank length. Whether it is true or not, I don't know, but something to consider any way.

    For my own experience, I did research crank length earlier this year when I had to replace my left hand crank. I had a short cranks outfitted with my trike on order under recommendation from the manufacturers. Unfortunately, it's a road bike chainset, 3 chain rings with 155 mm cranks, which seem downright impossible to find any more. I tried 170 mm cranks and to be perfectly honest, it was brutal on my knees. Of course, I have bad knees and at 5'2" (with 26" inseam) the range of flex I was doing with the longer cranks was not kind to my knees or in the interest of my best power delivery.

    Thankfully, I found a cycle shop in CA who had my chainset with the short cranks and all in back stock.

  10. #10
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    Speed bumps can be fun

    HI,
    i have a rather large bike and went over a tall speed bump seemed fairly straight forward until my right crank bottomed out on the peak of the speed bump, not a good feeling as the bike lifts up a bit into the air on the crank pedal talk about weird, i manged to come down with out crashing but it reallly hammered the crank..
    So I now coast with the pedals in the middle if there's a speed bump...

    most really bad wrecks seem to follow a crank bump, my guess is the energy of the bike is transfered back thru the crank to the object involved if its heavier , you go airborne.

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