Sheared crank arm bolt

hubcap
hubcap Posts: 163
edited March 2013 in Workshop
I've stupidly applied too much force to one of the bolts on my Ultegra crank arm and it has sheared off leaving about 3/4 of the bolt in place. Any tips on how I might go about getting it out, I'm guessing it's going to be a right job.

Assuming I can get it out I won't be able to get a replacement for a few days, would the bike be okay to ride with just the bolt on the opposite side in place and correctly tightened?

Or if I did want to ride the bike would it be best to leave the sheared off part still in there until I can get the replacement?

Any advice greatly appreciated.

Comments

  • Monty Dog
    Monty Dog Posts: 20,614
    Presume you mean one of the pinch-bolts on the non-drive arm? Either get your LBS to do this if you don't have the tools. Hold the crank securely in a vice and with a very sharp drillbit about 2.5mm try and drill into the end of the screw - the action of the drill may force it to unscrew. If not a screw-extractor to remove the remnants of the screw.
    Make mine an Italian, with Campagnolo on the side..
  • hubcap
    hubcap Posts: 163
    Yes that's the one, thanks for the advice.

    If I can't get it out straight away do you reckon the bikes okay to ride or will it cause damage to the crank arm?
  • cycleclinic
    cycleclinic Posts: 6,865
    I will be fine to ride as the bolt is tight. It is possible the bolt will not screw easily and it will have to be drilled out completey and a helicoil put in so a new bolt can be accepted. This is what good LBS are for.

    If you want to do this yor self you will need a good set of screw extractors as if these break you have had it and take your time. A vice is essential as well.
    http://www.thecycleclinic.co.uk -wheel building and other stuff.
  • desweller
    desweller Posts: 5,175
    thecycleclinic wrote:
    I will be fine to ride as the bolt is tight.

    This is bad advice. The screw needs the head to be present to generate the compressive load on the part. It isn't, so it can't; you're relying very heavily on the other screw, which is asymmetrically loading the crankshaft clamp. You might not damage the crankshaft but you stand a good chance of being stranded with a loose crank arm.

    I wouldn't ride it until you've got both screws in.
    - - - - - - - - - -
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  • crankycrank
    crankycrank Posts: 1,830
    Have you tried just using a metal pick to try to spin the bolt out? It may be fairly loose in the hole and could be coaxed out.
  • smoggysteve
    smoggysteve Posts: 2,909
    Get a tap and die set and drill it out.

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