"NY" wrote in message
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"Rob Morley" wrote in message
news:20181020233448.60296533@Mars...
On Thu, 18 Oct 2018 12:43:41 +0100
"Jim GM4DHJ ..." wrote:

yip 28 inch


English "28 inch" or German "28 inch"? There's half an inch difference
in the diameter of those.

So does Germany actually use "28" in the specification of its wheel
diameter? It must be one of the few measurements in the imperial system
that has survived Europe's use of the SI metric system. Are there any
other cases where items are sold in imperial units (as opposed to being an
integer number of inches which is translated into metric *)? If there is
1/2 inch difference in diameter of English and German 28" wheels, which
one is the true diameter that you would measure? Is one the external
diameter of the rim and the other the diameter of the tyre bead which is
slightly smaller and has to be levered over the rin?

Incidentally, has anyone actually had to use tyre levers for fitting a
bicycle tyre?

Yes, I used to more than half a century ago now when I used to ride one.

I always find that I just tuck the bead in at one side, then ease it in by
moving my thumbs towards the opposite side and then pull it away from the
rim at the very opposite until it pops into place; and vice versa for
removing. You'd think that a lever would be needed at least to make the
bead pop out from the rim when removing, but I've never found one
necessary. Am I unusual?

Yep, never encountered anyone doing it like that.

(*) For example I doubt whether 5 1/4 and 3 1/2 inch floppy and hard disks
are/were advertised that way in Germany, France etc - they'd be specified
in millimetres.