Tyre sizes

Brad Hubbard said:

Can someone explain what the two measurements in a tyre
size represent and what would be the difference between the
following?

(Diameter x Width? measured where?) 700x20c 700x25c 700x23c

The "700" refers to the outside diameter of the rim (which
is actually 622mm) and the tire. Obviously this isn't really
exactly 700mm unless you're running 39mm tires. It's an
archaic standard that doesn't really mean anything any more.
In fact, there were several different 700 standards (the one
that "stuck" being the 700c standard).

The diameter is normally measured across the widest part of
the mounted and inflated tire. However, the width of the rim
affects this measurement, and tire companies are all over
the place in manufacturing tires of a given "size". For
example, some 25mm tires are actually 23mm or less (a common
ploy since it makes your "25mm tire" look lighter than your
competitors "real" 25mm tire).

Mark Hickey Habanero Cycles habcycles.comhabcycles.comOpen ↗ Home of
the $695 ti frame

Mark Hickey said:

The "700" refers to the outside diameter of the rim (which
is actually 622mm) and the tire. Obviously this isn't
really exactly 700mm unless you're running 39mm tires.
It's an archaic standard that doesn't really mean anything
any more. In fact, there were several different 700
standards (the one that "stuck" being the 700c standard).

Thanks Mark,

That helps.

Cheers, Brad