I was surprised to find that even in Japan the normal tubing sizes for industry works out to be fractional inch size. I do think this comes from the British. The French work very hard to be different, so of course they have the true metric tubing size on their frames.
When I was working on headsets and BB for Specialized I had figure out the thread tolerances. The Japanese use JIS, very strict measurements for these threads. However, Campagnolo did not fit these standards during the early 1980's. So we went with the JIS for threads, Campi BB threads are a little larger. But we used Campi sizes for the headset races and cups. I measured something like 100 headsets to get this tolerance range as Campi would not give out their drawings. The range was quite large on the parts I measured. It was hard to determine what to say what the nominal sizes were supposed to be. Same thing is true with the hub freewheel threads, the tolerance is so large that the difference between Italian and English is kind of moot.
Jim Merz Bainbridge Is. WA
-----Original Message----- From: classicrendezvous-admin@bikelist.org [mailto:classicrendezvous-admin@bikelist.org] On Behalf Of goodrichbikes Sent: Monday, August 12, 2002 10:17 AM To: classicrendezvous@bikelist.org Subject: [CR]tubing diameters
Why and when did tubing manufacturers settle on non-metric sized outside diameters? For example- 1" or 25.4mm, 1 1/8" or 28.6mm, 1 1/4" or 31.8mm. Given that most of the tubes were or are manufactured outside of the U.S. why not pick a round number like 25mm, 29mm and 32mm? I know that the French and Davidson had their own non-standard diameters but most of the frames/bikes that we seem to be interested in on this list use 1", 1 1/8" and 1 1/4" diameter tubes. I don't think there's anything wrong with this just think it's historically odd. Any ideas?
Curt Goodrich Minneapolis, MN
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