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Thread: crank fail

  1. #1
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    crank fail

    hey all i broke my crank never seen it happen before and to be honest if some oen told me about it id have a hard time believing it. so here is a picture.


    was on a night ride bout a third of the way in when we hit a steep up hill. i missed the line so i turned around and re did the hill. my second or third pedal stroke i heard a pop. the bike was still moving so i figured it was something dumb. when i go to the top of the hill and looked at my bike, i realized the tight spot on my chain line had shifted. upon closer look i found that. It was an XT crank.
    so here the plan let see you crank, frame or single speed related failure.
    stumpjumper 29 evo
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  2. #2
    meatier showers
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    Looks like you ziptied it good as new.

    --sParty
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    Quote Originally Posted by riverrat
    Jaybo... quit *****ing and move to Texas

  3. #3
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    if shimano doesnt warranty that, i'd be pretty pissed as it's an obvious flaw

  4. #4
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    yeah i bought it used so im sure they wont cover it.
    stumpjumper 29 evo
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  5. #5
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    i am starting to distrust my four-bolt crank.

  6. #6
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    chainring position?

    Are those cranks designed to have the chainring running in the outboard position? Not sure it would or should make a difference, just curious.
    Cheers,
    M

  7. #7
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    Quote Originally Posted by idaz
    Are those cranks designed to have the chainring running in the outboard position? Not sure it would or should make a difference, just curious.
    Cheers,
    M
    honestly not sure they are designed to have three rings on them :P
    stumpjumper 29 evo
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  8. #8
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    Quote Originally Posted by mack_turtle
    i am starting to distrust my four-bolt crank.
    you just gave Sparty a boner.

  9. #9
    meatier showers
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    Quote Originally Posted by ISuckAtRiding
    you just gave Sparty a boner.
    That ain't sayin' much...

    Anyway the truth about cranks designed to employ 3 chainrings is this. The two non-granny rings are supposed to share the job of structurally supporting one another & the bolt circle. Take one ring away and bolt hole failure can happen more easily. Personally I'm not a fan of guard / bash rings, but at least these do the job that the 2nd ring was intended to do.

    {boing}

    --sParty

    P.S. 5 is better than 4. Sorry.
    disciplesofdirt.org
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    Quote Originally Posted by riverrat
    Jaybo... quit *****ing and move to Texas

  10. #10
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    Quote Originally Posted by Sparticus
    That ain't sayin' much... not hard to do.

    {boing}

    --sParty
    At your age?! I'm impressed!

  11. #11
    meatier showers
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    Quote Originally Posted by ISuckAtRiding
    At your age?! I'm impressed!
    Notice I edited the "not hard" part... those words strike fear into a guy my age... I'll be 57 on election day... I said *election* day... anyway, funny how age sneaks up on ya... I wasn't always this old.

    I keep tellin' myself it's the lucky ones who make it this far.

    Right?

    And I keep riding my bike like I'm in denial.

    Which I totally am.

    Okay, let's go back to talking about crank failure. Or is that what we were talking about all along?

    --sParty
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    you wanted to be.

    Quote Originally Posted by riverrat
    Jaybo... quit *****ing and move to Texas

  12. #12
    bi-winning
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    I've seen that happen to a couple of carbon cranks.
    When under pressure, your level of performance will sink to your level of preparation.


    Shorthills Cycling Club

  13. #13
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    I've seen this happen when a bolt/ bolts where not tight enough.
    Last edited by crazy8; 10-30-2010 at 02:27 PM. Reason: picture

  14. #14
    Drinking the Slick_Juice
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    cant go wrong with a 5 bolt square taper set for you next purchase
    "If women don't find handsome , they should at least find you handy."-Red Green

  15. #15
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    Can't go wrong with 4 bolts either as long as they're torqued to proper spec. I'ts also a good to use steel bolts rather than alloy on SS.

  16. #16
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    The only failure I see here is the public school system.

    That's right, I said it. Condemn.

  17. #17
    ballbuster
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    I'm going with....

    Quote Originally Posted by nickcarll
    hey all i broke my crank never seen it happen before and to be honest if some oen told me about it id have a hard time believing it. so here is a picture.


    was on a night ride bout a third of the way in when we hit a steep up hill. i missed the line so i turned around and re did the hill. my second or third pedal stroke i heard a pop. the bike was still moving so i figured it was something dumb. when i go to the top of the hill and looked at my bike, i realized the tight spot on my chain line had shifted. upon closer look i found that. It was an XT crank.
    so here the plan let see you crank, frame or single speed related failure.
    loose chainring bolts caused that. 4 arm, its especially important that they are all torqued down. One works loose, it puts a ton of strain on the remaining three. Personally, I use blue loctite on them to keep them from backing out.

  18. #18
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    I've seen two rings be destroyed by loose rings but never a crank.
    stumpjumper 29 evo
    Jabberwocky
    Gt peace 9'r
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