Friday, January 13, 2012

Some Weights and Measures

Some geeky technical specs to start your morning.

Thanks to one of the mechanics at the Recyclistas shop in Victoria, BC for this tip. It seems Sekine bikes have an odd 70mm bottom bracket shell size; but use the common 1.37"x24TPI threading. Many older road bikes would be the ubiquitous English-standard 68mm shell, although Italian BBs were also 70mm (with a different threading).
Not sure exactly how many of the bikes used the 70mm size, but they were probably on most models, at least up to 1979. Need to check some more frames.

1974, model SHT

1977, model SHL


Some more technical information. While I had the above pictured frames stripped down, I weighed them both. Both frames have the same lugs but predictably the mixte frame, with its plain steel and extra tubes, is 2lbs heavier. Here's the numbers:
20" Sekine SHT: frame 4lb 7oz, fork 1lb 10oz (Combined 6lb 2oz)
This was Sekine's second from top-of-the-line frame. Lugged, with chromed stays and fork. Built with butted Cromoly tubing and Shimano drop-outs and fork tips.
20" Sekine SHL: frame 6lb 8oz, fork 1lb 13oz (Combined 8lb 6oz)
This was Sekine's nicest mixte racer frame. Lugged, with chrome-dipped fork. Built with Canadian-made hi-tensile tubing, stamped dropouts.

4 comments:

  1. does this mean replacements are hard to find? Could you use a standard 68mm? would it need spacers?

    ReplyDelete
  2. I'd bet a normal Shimano-type cartridge bottom bracket would work alright. The plastic preload cup on the non-drive side will probably just thread in an extra little bit, which is fine because it doesn't have a shoulder.

    On older cup-and-spindle types, the lockring on the non-drive side cup will just be left with less thread to grab.

    ReplyDelete
  3. Would this crankset fit:
    http://www.nashbar.com/bikes/Product2_10053_10052_516642_-1

    with the 68mm GXP BB?

    ReplyDelete
  4. Not sure. Anything with a through-axle will probably depend on that 68mm shell, otherwise it won't preload bearings or seat on the spindle as designed. Might want to face 2mm off the BB.
    Your best bet would be to head into your local bike shop and get some advice.

    ReplyDelete