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  1. #1
    Senior Member
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    Jul 2008
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    Melbourne, FL
    My Bikes
    1988 Miyata 512 (retired), 2003 Specialized Stumpjumper, 1990's Bob Jackson ser#20602 (Messina, I think)
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    Cinelli-style sloping crown fork. Diagnosis please.

    Well, I bought this great Bob Jackson, used, this summer. Since then I've noticed very strong "speed wobble" except it happens even at like, 10 mph. Blazing fast, I know.

    I thought maybe the frame was too noodly or I was too fat. Today I read somewhere (maybe something from Jobst Brandt?) and someone mentioned they had a cracked fork and it made that type of wobble worse. Then I definitely read something by JB that said Cinelli-style internally lugged forks can crack. Then I'm thinking about how it sounds like my stem has been creaking/popping when I stand up to pedal...
    I looked over at my bike across the office...

    I rode carefully home and pulled the wheel out of the front fork and here's what I saw where the right leg meets the crown:

    and


    I am telling myself this is just a crack in the paint, but I fear it is the leg separating from the crown.
    What do you see?
    If the fork is trashed, would that have been causing my wobble problem or is that more a function of the geometry of the frame and fork?

    Help?

  2. #2
    Senior Member Nessism's Avatar
    Join Date
    Jun 2004
    Location
    Torrance, CA
    My Bikes
    Homebuilt steel
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    Not sure but looks like the fork blade is starting to separate as you noted. If that were my fork I’d retire it before it puts you on your head.
    Becareful buying/selling bike parts on-line. I learned the hard way. :(

    Good/Bad Trader Listing

  3. #3
    Member
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    Aug 2008
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    The first fork I built had that crown, and it is doing the same thing. I know for a fact that I didn't get it hot enough and that there is probably not 100% filler penetration. Fork has been going strong like that for a number of years. I would at the very least mark the ends of the cracks with a fine point sharpie so you can monitor the cracks, and more idealy, I would retire the fork. If you keep riding it, keep a close eye on it.

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