Self-loosening bottom bracket

Mystique
Mystique Posts: 342
edited April 2008 in Workshop
Out for a training ride the other night when it seemed to get harder & harder to pedal. Finally noticed that the Bottom Bracket (chainring side...) had managed to loosen itself. You'd have thought that the act of pedaling would, if anything, tighten that side rather than loosen it.

I've subsequently stripped & refitted the BB, but still can't fathom how it worked loose - I don't backpedal & the road surface wasn't especially rough.

Any ideas??

Comments

  • kilo
    kilo Posts: 174
    I read somewhere that Italian threaded bottom brakets have a reputation for loosening, a quick google produced this http://www.bikeforums.net/archive/index ... 56411.html
  • Mystique
    Mystique Posts: 342
    Hmmm...mines Italian threaded :(
  • Down the Road
    Down the Road Posts: 949
    Needs to fitted to the correct torque otherwise this will happen again
    Racing is life - everything else is just waiting
  • dennisn
    dennisn Posts: 10,601
    I've had an Italian BB for some time and haven't had this problem although I know it
    exists. I have had both the "standard" BB and outboard bearing.

    Dennis Noward
  • redddraggon
    redddraggon Posts: 10,862
    Try some loctite....might help in stopping it come undone.
    I like bikes...

    Twitter
    Flickr
  • dennisn
    dennisn Posts: 10,601
    Recently the bottom brackets that I have bought(octalink & Dura-Ace outboard) come with a coating on the threads which I can only assume is some form of Loctite.
    I have Italian BB's and can't recall having problems. Then again when I put in a BB
    I usually put some real a** behind it. And I have my share of that.
  • Smokin Joe
    Smokin Joe Posts: 2,706
    Mystique wrote:
    Out for a training ride the other night when it seemed to get harder & harder to pedal. Finally noticed that the Bottom Bracket (chainring side...) had managed to loosen itself. You'd have thought that the act of pedaling would, if anything, tighten that side rather than loosen it.

    I've subsequently stripped & refitted the BB, but still can't fathom how it worked loose - I don't backpedal & the road surface wasn't especially rough.

    Any ideas??
    The pedals may be turning in the same direction as the thread on the BB cup, but the bearings are turning anti clockwise inside the cup, which is why italian BB's are prone to loosening on the right side.
  • aracer
    aracer Posts: 1,649
    It's actually nothing to do with the direction any bearings are turning, but down to precession which is one tube moving around inside another slightly larger one (the threads of the BB inside the frame threads). That results in the inner tube rotating in the opposite direction to the applied force.

Categories