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  1. #1
    94109 Bakabon's Avatar
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    Schwinn Paramount Track Bike. Mechanic Question>>>Strange BB

    I would love to hear some explanation from any expert in Paramount P14...

    So I was building up my P14 last night.... the BB width measured 68mm which mean English threading. I have both English 68-P-120 and ISO 70P-120 ... Campy BBs.
    When I tried to install English BB cups, the threading seems not right, it would not go in. But the ISO cups does.... So I ended up installed ISO BB with 70 spindle. the lockring cup side does stick out 2mm than usual. the chain line is perfect... and spin very smooth...

    Also the headset is Italian headset that I installed and fit perfect.
    I don't understand... If the BB width measure exactly 68mm then it should be English...

    If anyone know why.. I would really appeciate any input..

    One thing I thought is that maybe BB threading has been rethread from English to ISO.. but why??

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    Quote Originally Posted by Bakabon
    One thing I thought is that maybe BB threading has been rethread from English to ISO.. but why??
    That's what I'm thinking, too - maybe a previous owner already had a nice expensive set of parts, and it was cheaper to rethread than to buy a new bottom bracket. Or maybe you've got a team issue frame, which might have been customized to accept a sponsor's parts.

    Anyway you've got a cool bike and I'm jealous.

  3. #3
    94109 Bakabon's Avatar
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    mmm I got to take it too LBS that know old bike...

  4. #4
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    English threading is ISO threading by definition, so either there's a problem in the threading of what you are calling the English-threaded cups or you started to cross-thread when you attempted to install the first cup.

    Italian threading for headsets differs from English threading only in the pitch of the threads, not the thread count per mm, so it's not especially surprising that an Italian headset was installed successfully on the Paramount.

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    By ISO did you mean (incorrectly) Italian threading?

    One way to salvage an English threaded bottom bracket shell with badly damaged threads is to ream it slightly oversize and retap it to Italian threads. Maybe that's what was done in this case.

  6. #6
    Gone, but not forgotten Sheldon Brown's Avatar
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    Quote Originally Posted by HillRider
    By ISO did you mean (incorrectly) Italian threading?

    One way to salvage an English threaded bottom bracket shell with badly damaged threads is to ream it slightly oversize and retap it to Italian threads. Maybe that's what was done in this case.
    ...But the O.P. said the English cup wouldn't fit in...Italian is considerably larger than English/ISO.

    If you try to install an English/ISO cup in an Italian bottom bracket, the cup will just fall through, won't engage the threads a-tall.

    It does sound as if he or she should have used the shorter spindle.

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  7. #7
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    Quote Originally Posted by Sheldon Brown
    ...But the O.P. said the English cup wouldn't fit in...Italian is considerably larger than English/ISO.
    Right, he did say it "wouldn't go in", not that it was too small. I'm still not sure if the threads didn't match or the cups bottomed out before they were all the way installed.

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    Quote Originally Posted by HillRider
    Right, he did say it "wouldn't go in", not that it was too small. I'm still not sure if the threads didn't match or the cups bottomed out before they were all the way installed.
    See post #4. In other words, there's no problem with the threading in the Paramount's bottom bracket (or fork, for that matter). The problem is that the "English" cup(s) has bad threads; either that or (more likely, in my experience) operator error (starting the cup at an angle so that it started to cross-thread).

    As Sheldon B. says above, the original poster should simply install the "English" bottom bracket spindle (the spindle intended for use with 68-mm bottom brackets) to get rid of that extra 2 mm of lockring-side BB cup sticking out and call it a day. While the spindle is out of the frame, I'd also try the "English" cups again if their threads pass close inspection under a strong light.
    Last edited by Trakhak; 04-22-06 at 08:59 AM.

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