Boardman Urban Crank Arm Falling Off

nickl360
nickl360 Posts: 59
edited June 2012 in MTB workshop & tech
So... I've cycled in to work today and the crank arm has come away from the bottom bracket, leaving me with a pedal attached to my foot by the cleat and away from the bike.

I managed to fit it back on at the roadside with my pocket tool but it doesn't seem to bite the bottom bracket at all anymore.

Would this be covered under warranty? Should I expect Halfords to fix the bike for free?

Comments

  • The Rookie
    The Rookie Posts: 27,812
    How old is the bike? That is fairly important in understanding if it's a warranty issue or not!

    What doesn't seem to bite the BB, your pocket tool, the retaining bolt or the crank arm, does it just spin or is it 'loose' and what BB type is it?

    Sorry for all the Q's but my Chrystal ball is in for servicing, not sure when I'm going to get it back.
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • nicklouse
    nicklouse Posts: 50,675
    they may fix it but checking bolts should be part of your routine maintenance.

    what cranks are they? i would get a proper allen key to do them up tight is Square taper/isis/powersplin/etc fitting.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • nickl360
    nickl360 Posts: 59
    Sorry, missed out the key bit of details in my original post.

    The bike was purchased in August 2011.

    I place the crank arm over the BB and tighten the two allen keys as tight as I can with my pocket tool and it's wobbly and will slide off if pulled on.

    The crank arm is a FSA Comet, does anyone have one of these? The teeth in the arm only go 2/3rds of the way in which I think is contributing to the problem.
  • turnerjohn
    turnerjohn Posts: 1,069
    you need to torque up the installation bolt on the non-drive side crank; goes into the axle. Make sure the bolts on the crank arm are loosened first. Torque the bolt will pull the crank arms together, only then do you torque the bolts on the non-drive side crank.
    If the bikes been servived recently you may have a case, however crank bolts are one the "check tight every ride" things.....
  • nicklouse
    nicklouse Posts: 50,675
    nickl360 wrote:
    Sorry, missed out the key bit of details in my original post.

    The bike was purchased in August 2011.

    I place the crank arm over the BB and tighten the two allen keys as tight as I can with my pocket tool and it's wobbly and will slide off if pulled on.

    The crank arm is a FSA Comet, does anyone have one of these? The teeth in the arm only go 2/3rds of the way in which I think is contributing to the problem.
    with this info I will answer this question.
    Would this be covered under warranty? Should I expect Halfords to fix the bike for free?
    No.
    "Do not follow where the path may lead, Go instead where there is no path, and Leave a Trail."
    Parktools :?:SheldonBrown
  • The Rookie
    The Rookie Posts: 27,812
    Isn't the Comet an external BB (rhetorical question....), have you pushed the driveside crank all the way in, the left hand arm doesn't attach to the BB it attaches to the axle which is part of the drive side crank......do you know what you're doing?
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • nickl360
    nickl360 Posts: 59
    In short... no. I'm going to the LBS to get it fixed this afternoon.

    It would make sense if the BB wasn't all the way through as it's not gripping properly.
  • XCtrailmachine
    XCtrailmachine Posts: 5
    have you checked inside the crank arm for any dents or imperfections??? this may be a large contributing factor.
    Voodoo Hoodoo 2011
  • The Rookie
    The Rookie Posts: 27,812
    The BB is screwed into the frame, it doesn't go through anything. The axle goes through the BB and is part of the drive side arm.
    Currently riding a Whyte T130C, X0 drivetrain, Magura Trail brakes converted to mixed wheel size (homebuilt wheels) with 140mm Fox 34 Rhythm and RP23 suspension. 12.2Kg.
  • nickl360
    nickl360 Posts: 59
    Well it looks like I'm missing a screw cap hence why it's falling off. I've left it with them to sort.
  • oxocube1
    oxocube1 Posts: 651
    By the sounds of it, the spline inside the crank arm has started to round off which is the reason why it keeps coming loose when you tighten it. I have had a customer with this problem with at least one Comet chainset in the shop before. If the bolts loosen slightly, the arm therefore becomes a little loose and if the bike is ridden in this state, the arm will rattle and move causing the spline to round off. It would help to have the missing screw cap, but it should not really be an issue as the crank arm is held on primarily by the two pinch bolts.

    To answer you question about warranty, unfortunately it would not be covered. As has been said somewhere above, tightening the bolts and cleaning etc. is part of a standard maintenance regime and parts are not covered if they are not maintained. However that is just the way it is supposed to work, if you go back into the Halfords you got it from, they may say they will 'get it done under warranty'. It just depends on how well they know the warranty procedures. If you still have it, the third page in the booklet you got with the bike will explain the warranty stuff :).
    2016 Banshee Rune

    2012 Nukeproof Mega
    2011 Haro Flightline Expert
    2010 Spesh FSR XC Pro
  • nickl360
    nickl360 Posts: 59
    I picked the bike up yesterday, all fixed and there was no charge. Excellent service..

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