An anonymous poster wrote:
> Hi if I am not mistaken.... MTB stem clamps are
> 25.4mm dia.=20
Yes, that is the ISO standard size for all types of
bicycles, a.k.a. 1 in=
ch.
> Roadbike quill stems used to be the same but when changed
> to threadless system went to a 26.0mm dia. clamp.=20
No, there's no connection with threadless, that has to do
with the other =
end of the stem, the way it fits on the fork.
Both quill and threadless stems are readily available in
both 25.4 and=20 26 mm sizes. The selection is much better,
however, in the ISO=20 standard 25.4 size.
Before the ISO standards were promulgated, there were a
variety of=20 national sizes for handlebar/stem clamps, and
also some proprietary ones =
used by specific manufacturers (Cinelli, Titan.)
Because some Italian brands of stems and handlebars were
popular for=20 high-end road bikes, the Italian 26.0 mm
standard is often used as a=20 secondary size standard for
drop handlebars, but most drop bars on the=20 road are
actually 25.4.
> They are now doing 31.8mm dia clamps which are indicated
> as oversized.
c.h.a. 1 1/8"
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