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Broken crank, advice please

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  • 04-08-2006 11:50am
    #1
    milod
    Closed Accounts Posts: 757 ✭✭✭


    hey folks, some advice needed here...

    My crank arm sheared off last night while cycling (drive side) :mad: The bike is a specialized Sirrus sport, 2 years old with maybe 8k on it. I put some serious torque through the pedals admittedly but I rarely stand up on the pedals (except on Knockmaroon hill , last night...). I also use the gears, I don't start off in 5th standing up etc. so the question is, is this normal wear and tear? can I complain to the bike shop? does this happen to others? etc etc


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    #2
    Idleater
    Registered Users Posts: 6,236 ✭✭✭Idleater


    milod wrote:
    My crank arm sheared off last night while cycling (drive side)

    did the whole crank just come off the bottom bracket?

    if you look at the BB axle it should be square (with rounded corners) and the crank should have a corresponding square hole in it.

    If either of these are non square then it has sheared. In htis case, if you put the crank back onto the BB it would "spin" around.

    I doubt this is the case.

    I would hazard a guess that in fact the bolt that holds the crank onto the BB has come out which has allowed the crank to come off.

    Go to your local bike shop and get them to fit a new retaining bolt to hold the crank in place.

    BTW, I hope you didnt do yourself too much damage when the crank came off while you were riding it!!! how did you get home?

    L.


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    #3
    Ghost Rider
    Registered Users Posts: 1,883 ✭✭✭Ghost Rider


    This happened to me last year upon taking off from a set of traffic lights. The crank snapped and I flew over the handlebars. I managed to get up in time to avoid getting run over by a motorcycle coming from behind me but I had fractured a bone in the top of my finger in the fall.

    I couldn't believe the thing just snapped. When I bought a new one and explained what had happened to the guy in the shop, he expressed surprise but didn't go as far as to admit that that should never happen to such a crucial component on a bike.
    milod wrote:
    hey folks, some advice needed here...

    My crank arm sheared off last night while cycling (drive side) :mad: The bike is a specialized Sirrus sport, 2 years old with maybe 8k on it. I put some serious torque through the pedals admittedly but I rarely stand up on the pedals (except on Knockmaroon hill , last night...). I also use the gears, I don't start off in 5th standing up etc. so the question is, is this normal wear and tear? can I complain to the bike shop? does this happen to others? etc etc


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    #4
    Itsfixed
    Registered Users Posts: 564 ✭✭✭Itsfixed


    nereid wrote:
    did the whole crank just come off the bottom bracket?

    if you look at the BB axle it should be square (with rounded corners) and the crank should have a corresponding square hole in it.

    If either of these are non square then it has sheared. In htis case, if you put the crank back onto the BB it would "spin" around.

    I doubt this is the case.

    I would hazard a guess that in fact the bolt that holds the crank onto the BB has come out which has allowed the crank to come off.

    Go to your local bike shop and get them to fit a new retaining bolt to hold the crank in place.

    BTW, I hope you didnt do yourself too much damage when the crank came off while you were riding it!!! how did you get home?

    L.
    If your bike is two years old it may have an shimano octalink bb or an ISIS bottom bracket rather than the square tapered type as described by nereid.

    But again, i think the most likely cause is the bolt holding the crank to the bb must have come off or loosened, causing the crank to fall off. If it has sheared off, then take a look at the groves around the edges - if they are stripped, then thats your problem.


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    #5
    8kvscdpglqnyr4
    Closed Accounts Posts: 413 ✭✭8kvscdpglqnyr4


    This same thing also happened my a couple of years ago - crank just snapped. I didn't injur myself but it could have been omre serious.

    At the time I did some searching on the Shimano website and sure enough, the part had been recalled. I got a full replacement from Shimano UK.

    I can't find the exact link now, but I came across this:
    http://www.cpsc.gov/cpscpub/prerel/prhtml97/97149.html


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    #6
    milod
    Closed Accounts Posts: 757 ✭✭✭milod


    nereid wrote:
    did the whole crank just come off the bottom bracket?

    Nope, the crank broke off where it attaches to the chainring which is a single casting - i.e. the crank arm is part of the entire cast not a separate item...

    thx anyway for the advice


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    #7
    milod
    Closed Accounts Posts: 757 ✭✭✭milod


    Julia Melted Waterfall wrote:
    This same thing also happened my a couple of years ago - crank just snapped. I didn't injur myself but it could have been omre serious.

    At the time I did some searching on the Shimano website and sure enough, the part had been recalled. I got a full replacement from Shimano UK.

    I can't find the exact link now, but I came across this:
    http://www.cpsc.gov/cpscpub/prerel/prhtml97/97149.html

    Hey thanks for that!, it is a Shimano crank, but not one of the model numbers mentioned. But I reckon I'll try my luck with Shimano UK for the craic...


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