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  1. #1
    <3s bikes Re-Cycle's Avatar
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    two questions: crown race fit and oversized seatposts

    While replacing a kinked frame/fork for a friend I recently encountered two things I've never encountered before. Background is that a friend of mine who commutes on a Columbus tubing faggine hit a pot hole and bent the head tube lugs on the frame. Fortunately I found him a similar sized bertoni frame / fork but here's where the problem(s) occurred.

    First off while switching the threaded chris king headset to the new frame, I noticed that the greased crown race basically slipped right on without having to be set. Obviously both forks are off Italian 1" steer tubes, how can that be? Beyond that the chris king headset had only been installed once [not worn out] and the shimano 600 crown race that came off the bertoni fork took the usual amount effort to remove so I can't blame the fork for being worn down.

    Ok, next problem, every single 27.2 seatpost including the one that came out of the faggine was to small. The clamp touched just as enough clamping force was being applied to the post. Its possible that someone previously tried to force a larger post in to the bertoni but I didn't see any bulging on the seat tube. Can I get a 27.2 oversize post? I can't imagine that a 80's Columbus matrix frame used anything larger then a 27.2 by default but I could be wrong.
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  2. #2
    Old fart JohnDThompson's Avatar
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    Quote Originally Posted by Re-Cycle View Post
    First off while switching the threaded chris king headset to the new frame, I noticed that the greased crown race basically slipped right on without having to be set. Obviously both forks are off Italian 1" steer tubes, how can that be? Beyond that the chris king headset had only been installed once [not worn out] and the shimano 600 crown race that came off the bertoni fork took the usual amount effort to remove so I can't blame the fork for being worn down.

    Ok, next problem, every single 27.2 seatpost including the one that came out of the faggine was to small. The clamp touched just as enough clamping force was being applied to the post. Its possible that someone previously tried to force a larger post in to the bertoni but I didn't see any bulging on the seat tube. Can I get a 27.2 oversize post? I can't imagine that a 80's Columbus matrix frame used anything larger then a 27.2 by default but I could be wrong.
    The nominal diameter of the crown race seat on an Italian fork is 26.4mm; the nominal ID of the headset crown race is 26.3mm; they should be a tight press fit. If the race slides on easily, one or the other is out of spec. If the race seat on the fork is undersize, it can be knurled to build it up to spec. If the ID of the crown race is oversize, replace it.

    Re: the seat post -- it sounds like someone may have been overly aggressive in reaming the seat tube. You can get 27.4mm posts that should solve the problem.
    Last edited by JohnDThompson; 02-13-09 at 01:31 PM.

  3. #3
    AEO
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    Senior Member AEO's Avatar
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    could be a 27.4mm seat post.

    headset crown race diameter, there's more than one. http://www.sheldonbrown.com/headsets.html

    it's best if you can get your hands on a set of calipers from the hardware store and measure them.
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