Curt Goodrich asked:
>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.
But mostly in England, which only went metric in the 1970s!
>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?
This goes back probably a hundred years or more. Most of the standards in use today originated with B.S.A. in the early years of the 20th century. British industry didn't do anything metric back then. This is also why bearing balls are all inch-based sizes.
As long as lugged construction was the norm, folks were pretty well locked into standard size tubing to fit standard size lugs.
This changed beginning in the 1970s with the BMX boom and the use of T.I.G. welding. This technology, among other things, migrated from BMX to MTB construction later on.
Sheldon "Momentum" Brown
Newtonville, Massachusetts
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