Left crank coming loose

samg123
samg123 Posts: 275
edited June 2012 in Workshop
Went for a 120 miler yesterday and had to stop three times to tighten the left hand crank, which was coming loose and shaking around (thought it was a cleat issue at first until I noticed the whole thing was moving!) It's a square taper, so fastened with a bolt. My question is: what is buggered? BB or crank?

Comments

  • freezing77
    freezing77 Posts: 731
    Almost certainly the crank.
    Soft aluminium V hardened steel
  • Rodders30
    Rodders30 Posts: 314
    Mine used to do this.

    Degreased thread and both tapers. Put back on with fresh thread locker and been fine ever since.
    Trek 1.5 Road
    Haro MTB
  • Barteos
    Barteos Posts: 657
    There's a chance that the taper (crank) may be already slightly rounded and the problem may come back.
    For quite a long time I used to think that square tapers should be kept dry but the correct practice is to very lightly oil/grease them. Keeping them dry like with any other hardware makes it difficult or impossible to feel or measure the required torque.
  • Slack
    Slack Posts: 326
    Rodders30 wrote:
    Mine used to do this.

    Degreased thread and both tapers. Put back on with fresh thread locker and been fine ever since.

    +1 make sure both faces are totally clean before installation.
    Plymouthsteve for councillor!!

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