On 18/10/2018 17:45, NY wrote:
"Chris French" wrote in message
...
There are two different '28 inch ' tyre sizes though,Â* those with
a bead diameter of 635mm, otherwiseÂ* known as 700B and those with
a bead diameter of 622 mm, otherwise known as 700C.

You can also get different '26 inch' tyres as well.

Which is why it's always better to refer to tyre size by their ISO
sizes, as no confusion then


One thing about ISO sizes bewilders me: why do they specify the height
of the tyre (OD - ID) as a percentage of the width? Seems an odd way to
do it. Surely the three measurements that need to be specified
explicitly a inside diameter (ie diameter of wheel and of bead),
outside diameter (ie of tread) and width. And preferably specify all
three in the same bloody units - either all in mm for Europe (and
*maybe* UK) or else all in inches (for US) - not some half-arsed mixture
of the two.

Similar to car tyres then? 205/55R16 has a sidewall height of 55% of
205mm on a 16" rim. If the second figure is missing, such as 185R13,
then the height is 80% of the first figure.

SteveW