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  1. #1
    put me back on my bike stewartp's Avatar
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    Scientific Method

    "The real purpose of scientific method is to make sure Nature hasn't misled you into thinking you know something you don't actually know" - Robert Persig, Zen and the Art of Motorcycle Maintenance.

    I was convinced the bottom bracket on my Airbourne was giving up. This was disappointing because it was a Campag Centaur with only 3000 klimotres on it.

    The symptoms was an intermittant tick/rumble when pushing hard on the cranks when climbing a hill. It didn't happen when I stood up on the pedals.
    It got worse and worse until it happened on every pedal stroke, and even on the slightest gradient. It didn't do it when the bike was under no load so I couldn't get it to happen on the bike stand.

    The sound definitely seemed to come from the bottom bracket.
    And because it occurred when pushing hard on the cranks, and not when coasting or cruising on the flat, I was sure it was the BB.

    I shelled out for a new botom bracket and tool to remove it. Did the replace and stripped and cleaned up the chainrings while I was at it. The old BB was rusty on the outside and had a slight "notchy" feel. I was convinced I'd cured the problem.

    Imagine my dissapointment to find no change.

    Further investigation reveals the fault to be with the saddle!! (or perhaps seat post) I can get the same tick without pedalling and just rocking back and forward on the saddle!

    When I climb hills in the saddle I must be shifting my position on the saddle slightly, and rocking too, whereas cruising I must use a more balanced "circular" pedalling motion.

    doh!

    Stew
    Last edited by stewartp; 09-03-02 at 11:18 AM.
    The older I get the better I used to be.

  2. #2
    NCAA - DUAL CHAMPIONS! a2psyklnut's Avatar
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    Well, it was about time to replace the bb anyways, now you've got the tools, the experience and keep the old bb as a backup!

    Money well spent Regardless!

    L8R
    "Life is not a journey to the grave with the intention of arriving safely in a pretty and well preserved body, but rather to skid in broadside, thoroughly used up, totally worn out, and loudly proclaiming, "WOW, What a Ride!" - unknown
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  3. #3
    DEADBEEF khuon's Avatar
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    Originally posted by a2psyklnut
    about time to replace the bb anyways
    At only 3000km?

  4. #4
    Infamous Dumpster Diver Buddha Knuckle's Avatar
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    Same thing happened to me, only I what I thought was a BB click was actually...a broken frame! You'd think that would be obvious, but that BB is like a mysterious black box. You could convince yourself that dwarves lived inside it if you had never seen the inside of one.

    Evil bottom brackets...

    BK
    Got my helmet on, you can't tell me I'm not in space
    -Kool Keith

  5. #5
    Wood Licker Maelstrom's Avatar
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    Wow I replace a bb every 2000 km. Sometimes sooner depending on how rough I am.

  6. #6
    Slow Moving Vehicle Jean Beetham Smith's Avatar
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    Geeee, every 2000 km? Poor "Little Pony" has 3093 miles=4977km, and I haven't heard a peep from her BB. Maybe I better listen harder.

  7. #7
    put me back on my bike stewartp's Avatar
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    I'd hope and expect to get 10000 out of a good Campag BB. Which is why I was disappointed when I thought it was collapsing after only 3000.
    Especially since all my cycling is road and I'm not huge. (ducks as he makes reference to a Rants & raves thread)

    Stew
    The older I get the better I used to be.

  8. #8
    The Flying Scot chewa's Avatar
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    The other week my friend had a weird clicking coming from his bike. It dissapeared if he sat back and came back when he got on the drops.

    After two stops to adjust everything in sight we noticed it was the zip pull on his jacket hitting the top tube.
    plus je vois les hommes, plus j'admire les chiens

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  9. #9
    put me back on my bike stewartp's Avatar
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    That's EXACTLY what I'm getting at. I hate when that happens.

    Squeaky pedal cleats also cause panic attacks.

    On my motorcycle I had a helmet with a visor that used to "ping" intermittantly in turbulent air. It sounded just like a metallic tick from the bars/forks/front end.

    Also I've often had a terrible fright when roadworkers let rip with their pneumatic drill just as I'm wondering if there's a noise coming from the gearbox!

    Stew
    The older I get the better I used to be.

  10. #10
    DEADBEEF khuon's Avatar
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    Originally posted by chewa
    After two stops to adjust everything in sight we noticed it was the zip pull on his jacket hitting the top tube.
    The origin and direction of a sound while on the bike can be so confusing. Once on a ride, I had a ticking noise that I thought was coming from my headset so I loosened the stem bolt and tried retightening it... didn't help... then I thought it was maybe a spoke or my hubs. The spokes were all tensioned properly. The sound only occurred when I hammered out of the saddle. I eventually realised it was coming from the zipper-pull of my jersey.

    While on the STP, I was riding behind some guy who I thought was dragging his brakes. The noise was horrible... Then I realised it was occurring even when he wasn't braking. It was coming from his freehub! The thing sounded like it was about to detonate any minute. After a few miles, I decided to pass him because I couldn't take the noise any longer. It was a grinding/grating type of noise on the same level as nails across a chalkboard and it occurred anytime he freewheeled. I noticed that not many people rode around him for very long... poor guy. The bike looked in otherwise good condition.

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