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Pedalling Squares - Mystery Noise??

chrisgalchrisgal Posts: 130
edited May 2014 in Workshop
Having largely put new components on my bike I was getting a clunking noise around the BB/Crank when turning the pedals on the workstand.

After checking and double checking everything I couldn't find any obvious issues. I then came across the following on another forum which is the only solution left that I can think of.

"What you describe are the classical symptoms of pedaling squares. Pedaling squares means letting the upper run of the chain go slack at top and bottom dead center of the crank, then snapping it back into tension. That snap produces the "mysterious knocking sound."

Anyone know any mechanical solutions that I could try to correct this or any other potential reasons, other than bb, loose bolts problems. It only happens on the large chain ring.

Posts

  • styxdstyxd Posts: 3,234
    I pedal both squares and circles and have never had such a noise.

    It could be something up with your freehub.
  • DiscoBoyDiscoBoy Posts: 905
    It'd be quite the challenge to pedal squares by hand on a workstand...
    Red bikes are the fastest.
  • chrisgalchrisgal Posts: 130
    i'm nearly 100% it's not the freehub it's definitely coming from the crank/BB area. The BB is solid as a rock
  • chrisgalchrisgal Posts: 130
    DiscoBoy wrote:
    It'd be quite the challenge to pedal squares by hand on a workstand...

    "Pedalling Squares" was just the terminology I used from the forum I read as it described the only thing I can think that is happening in this case.

    I should maybe clarify further:

    1. The chain is on either large or small ring (just checked as I thought it was only the big ring but it's not).
    2. Start turning the cranks at a steady pace
    3. When I start decreasing the speed I turn the cranks then the 'clunking' noise begins. The noise is definitely coming from the crank/bb area.

    I'm perplexed!!! :(
  • chrisgalchrisgal Posts: 130
    Back from a couple of days working away and still trying to solve this issue……….unsuccessfully!!

    I've posted a video here (the sound seems to have faded but you can hear ok if using earphones)

    http://s91.photobucket.com/user/chrisgalw/media/Bit%20and%20Bobs/crank%20video/IMG_0862_zps8181b4f1.mp4.html

    If anyone has any ideas or solutions they would be gratefully accepted and would contribute massively to saving my sanity! :shock: :?
  • wishitwasallflatwishitwasallflat Posts: 2,923
    Don't mean to be funny but that sounds to me like the noise of bike stand feet rocking on a wooden floor. Does the noise happen off the stand when riding - if not then try turning the bike upside down and spinning the cranks to eliminate.
  • chrisgalchrisgal Posts: 130
    Don't mean to be funny but that sounds to me like the noise of bike stand feet rocking on a wooden floor. Does the noise happen off the stand when riding - if not then try turning the bike upside down and spinning the cranks to eliminate.

    Lol.....nope definitely not the stand.
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