I always found a great irony in the adoption of the ISO bicycle standards in that they adopted an obsolete and inconsistent set of specs.
By that I mean, they were in English units, which the champions of international standardization had at that time already been decrying for two decades as archaic and illogical. Yet they rejected the purely metric French standard to adopt one whose dimensions were in inches, or in thinly disguised inches converted to millimeters carried to three decimal places.
In terms of pure scientific logic, French thread would have been superior, as all dimensions were metric, and usually in whole millimeters. Even better, technically, would have been Swiss thread, identical to French except that the fixed cup is left hand thread, which of course is the technically correct design.
But market share and installed base won out over technical considerations, and those great champions of the SI system installed a standard that will preserve the English system they so frequently badmouthed, at least in the limited area of bicycle threading.
Regards,
Jerry Moos Big Spring, TX
Mark Stonich <mark@bikesmithdesign.com> wrote:
At 9/11/2006 09:56 PM -0400, Bradford Riendeau wrote:
>To add to what has already been said, the changeover was part of a
>movement in the early 1970's to establish ISO standards for bicycles.
>Fred DeLong who wrote for Bicycling chronicled the process at the
>time. If I remember correctly, English steerer tube (25.4 o.d .and
>22.2 i.d. aka 1 inch and 7/8ths), bottom bracket (1.37 x 24 tpi)
>and freewheel threading won out (1.37 x 24 tpi), in part because
>there were also the Japanese standards. The only standard that
>didn't fully stick was the stem pinch bolt standard of 25.4. The
>industry standard for road bars stuck with the Italian 26.0 until
>recently, although 25.4 is standard for mountain bars and a lot of Nitto stuff.
It's been a long time, and the brain cells are dying off ever faster, but; I seem to remember that the standards committee had two other recommendations that never got much traction.
One that never was taken seriously, was that pedal threads should be 1/2".
The other was that front hub "over lock nut" spacing should be 95mm. I believe some manufacturers may have retooled to meet this. I've found several front hubs from that era with narrower than normal bodies, and either spacers or very thick locknuts to bring the width out to 100mm.
These are very handy for building a "Modern" front wheel for an old Moulton or English 3 speed. (I'm well equipped to do a proper job of respacing frames and forks, but I prefer not to.) With carefully chosen cones and locknuts, I've gotten width down to 90mm or so.
If I've misremembered any of this, I'd welcome more solid info.
Mark Stonich;
Minneapolis Minnesota
http://mnhpva.org
http://bikesmithdesign.com