1970's Schwinn Varsity Bottom Bracket

Discussion in 'Singlespeed' started by jackfrost9p, Dec 23, 2007.

  1. jackfrost9p

    jackfrost9p New Member

    Joined:
    Dec 23, 2007
    Messages:
    4
    Likes Received:
    0
    Hi, I have a old Varsity and I want to convert it to a fixie. I wanted to replace the one-piece crank with a 3-piece crank. I bought a adapter from FMF:

    http://fmfbmx.com/Merchant2/merchant.mvc?Screen=PROD&Product_Code=425592050&Category_Code=BB

    That converts the "American" bottom bracket to a "Euro" bottom bracket, and it fits into the shell. But now I am confused on what size bottom bracket to buy.

    Here are the length's I measured, if you need more please let me know.

    The adapter is 24TPI, with a 1.370" hole.
    The shell of the Varsity is 65mm wide.

    This is where my confusion is, since it seems like all the bottom brackets are either 68mm or 73mm. I was thinking of adjusting the adapter to 68mm wide, there for it would stick out 1.5mm on each side. Then machining a washer 1.5mm wide that would fit between the frame and the adapter.

    If you know of any other options or comments on my current idea that would be greatly appreciated. Thanks.
     
    Tags:


  2. alfeng

    alfeng Well-Known Member

    Joined:
    Jul 23, 2005
    Messages:
    6,723
    Likes Received:
    126
    The Ashtabula/(American)-to-Euro adapter is meant to use a "standard" BRITISH threaded bottom bracket that fits in a 68mm/(ROAD) bottom bracket shell.

    The "lips" on the insert make up the difference in the width that you are concerned with ... THE ONLY THING YOU HAVE TO BE AWARE OF IS THAT ONE SIDE HAS A LEFT HAND THREAD (the drive-/crank side) & THE OTHER SIDE HAS A RIGHT HAND THREAD (the non-drive side).

    So, you can choose-and-use a Shimano square taper (UN-xx cartridge) BB, a Shimano Octalink BB, an ISIS BB, a Campagnolo square taper or UT, an FSA MegaExo, etc. as long as it has the British threading.

    The 73mm bottom brackets usually come with spacers that allow you to them in frames with 68mm wide shells.
     
  3. jackfrost9p

    jackfrost9p New Member

    Joined:
    Dec 23, 2007
    Messages:
    4
    Likes Received:
    0
    Thank you very much, that makes sense.
     
  4. jackfrost9p

    jackfrost9p New Member

    Joined:
    Dec 23, 2007
    Messages:
    4
    Likes Received:
    0
    Since I am making a fixie, I can use a bottom bracket with a shorter spindle length right? What length would you suggest?

    Thanks
     
  5. alfeng

    alfeng Well-Known Member

    Joined:
    Jul 23, 2005
    Messages:
    6,723
    Likes Received:
    126
    Yes-and-No ...

    AFAIK, only the traditional square taper (either "Shiimano"/Japanese or Campagnolo/Euro) spindles + ISIS are available in shorter lengths ...

    And, a majority of the square taper cranks were designed for asymmetrical spindles ... whereas, the shorter than 113mm spindles are designed for PISTA/(track) or BMX crankarms and are, AFAIK, symmetrical.

    If you mount a ROAD crank on a PISTA-or-BMX spindle, your crankarms will not be equidistant from the centerline of the bike ... the amount of offset doesn't justify moving the chainring more toward the bike's centerline -- adjustments to the chainline are usually implemented by mounting the chainring on the inner shoulder of the crankarm & sometimes, supplemented with a "bashring" on the outer shoulder.

    So/(FWIW), IF YOU DON'T ALREADY HAVE A CRANK, I would just go with a 113mm Shimano UN-51_or_better BB + almost any 90s-vintage Shimano square taper crankset.
     
Loading...
Loading...