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  1. #1
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    Broke a crank arm today

    Broke a crank arm today-img_1349.jpg

    Just got bike back from shop having the rear brake "looked" at and pads replaced. Was half way through a 12 miler when crossing a blacktop road my foot came off the pedal with the pedal and arm still attached to my foot. Sure am glad it happened like this than during a climb. looks like back to the shop to me.
    2013 Specialized Carbon Camber Pro 29er (Warranty frame and other stuff)
    2011 Specialized Stumpjumper Comp 29er

  2. #2
    Big Gulps, Alright!
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    Looks like it came off because it wasn't torqued properly, but it doesn't actually appear broken (although it's probably damaged beyond repair at this point).

  3. #3
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    Never been touched since I bought the bike so not sure how that could have happened. Do they come loose over time, like years?
    2013 Specialized Carbon Camber Pro 29er (Warranty frame and other stuff)
    2011 Specialized Stumpjumper Comp 29er

  4. #4
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    Quote Originally Posted by sgtjim57 View Post
    Never been touched since I bought the bike so not sure how that could have happened. Do they come loose over time, like years?
    Yes. You should make it a habit to check nuts and bolts on the bike after the first few rides and periodically throughout the life of the bike. You'd be surprised how many pedals, crank arms and chainring bolts are loose on bikes I repair at work.

    *edit* I was a bit disappointed when I opened this thread and did not see a "broken" crankarm...just one that fell off due to negligence BTW....how long did you ride that bike NOT noticing it was loose...?
    Mountain bikers who don't road ride have no legs...
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  5. #5
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    I have a Camber that I have been riding for more than a year so this one has sat without use. Camber is being repaired so I had to break out the back up. I would think I would have known it was loose but I guess I missed that while riding. It's been ridden by friends during this time and i have ridden it also a few times.
    2013 Specialized Carbon Camber Pro 29er (Warranty frame and other stuff)
    2011 Specialized Stumpjumper Comp 29er

  6. #6
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    Actually as you can see in the picture the arm failed, the bolt is still in the bottom bracket and it is still tight.
    2013 Specialized Carbon Camber Pro 29er (Warranty frame and other stuff)
    2011 Specialized Stumpjumper Comp 29er

  7. #7
    Elitest thrill junkie
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    Quote Originally Posted by sgtjim57 View Post
    Actually as you can see in the picture the arm failed, the bolt is still in the bottom bracket and it is still tight.
    That looks like the self-extracting ring, not the bolt.
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

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  8. #8
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    Quote Originally Posted by Jayem View Post
    That looks like the self-extracting ring, not the bolt.
    That is exactly what Mark at MOAB said when he looked at the bike and tyhe crank arm. Nothing to do with maintenance, bolt tightening or anything I as a user could have done just riding. Left it for them to repair, picked up my Camber Comp 29er after a warranty replacement on the rear triangle. thanks MOAB
    2013 Specialized Carbon Camber Pro 29er (Warranty frame and other stuff)
    2011 Specialized Stumpjumper Comp 29er

  9. #9
    Elitest thrill junkie
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    Well, the self extracting bolt doesn't hold the cranks on, it only comes into play when you try to take them off, but it remains on the crank (like in your picture) What is the condition of the actual anchoring bolt? Did it shear? That would be a "failure". A highly marred or even un-worn bolt would indicate it was loose.
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

    You're turning black metallic.

  10. #10
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    Bikes still at shop so I will have to add when I get it back. The bolt appeared to be fine, the mechanic said it was. Only the self extracting bolt failed and if it doesn't do anything not sure why that happened.
    2013 Specialized Carbon Camber Pro 29er (Warranty frame and other stuff)
    2011 Specialized Stumpjumper Comp 29er

  11. #11
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    I'm guessing something was loose and you didn't know it. It's probably come loose over time, especially if you haven't touched it since it was new. I'd bet the crank arm was loose but the bolt was still partially threaded in the spindle, and when you started pedaling hard it just sheared that self extracting bit to pieces.
    Mountain bikers who don't road ride have no legs...
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  12. #12
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    That's happened time and time again in the history of MTB Good that you got it fixed.

    The self-extracting bolt is not needed for anything but extracting, it could be removed, and before self-extracting bolts were the "norm" we used crank-pullers that threaded in there and pushed against the spindle. Now with hollow spindles that's not possible, but self-extracting bolts were already invented so it was a good idea to use them for the taper-lock external BB cranksets like Truvativ and Race Face.
    "It's only when you stand over it, you know, when you physically stand over the bike, that then you say 'hey, I don't have much stand over height', you know"-T. Ellsworth

    You're turning black metallic.

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