Why not use ETRTO?

[Profpointy]

Your local pubs use those new fangled pints? Real pubs still sell a furlong of beer in a fathom glass.

There is the furlong, firkin, fortnight system of units. Not wholly inconvenient as a microfortnight is about 1.2 seconds and a velocity of 1 furlong per fortnight is very close to 1 cm per minute

Note that firkin in this system is used as unit of mass: that of a firkin of water, thus 90lbs

 

[Dogtrousers]

Properly, 700C doesn't exist.

It should be 700x28C or similar.

The 700 is the overall diameter of wheel plus tyre in mm. The 28 is tyre width, and the letter is a code for the rim width, with C being by far the most common for road bikes.

I'm pretty sure that's wrong. Not 100% sure because "700C" is such a rubbish term there's no authoritative reference. I just know this from reading various (possibly wrong) websites over the years. There is a consensus.

The C refers to the tyre size, not rim width. Rim width is always sensibly given in mm.

A "C" tyre would therefore be 39mm (2x39 + 622 = 700). If you fitted one of those, if they existed, which they don't, to a 622mm rim you'd get a diameter of 700mm. Which tells us that most road bikes that are advertised as having "700C" wheels don't actually have clearance for a 700mm diameter wheel at all.

A 622mm rim with a 28mm tyre would have a diameter of 678mm if tyre sizes were reliable, which they aren't.

So the 700 in 700C is completely meaningless. Why not just give the bead diameter of 622?

 

[Alex321]

I'm pretty sure that's wrong. Not 100% sure because "700C" is such a rubbish term there's no authoritative reference. I just know this from reading various (possibly wrong) websites over the years. There is a consensus.

The C refers to the tyre size, not rim width. Rim width is always sensibly given in mm.

A "C" tyre would therefore be 39mm (2x39 + 622 = 700). If you fitted one of those, if they existed, which they don't, to a 622mm rim you'd get a diameter of 700mm. Which tells us that most road bikes that are advertised as having "700C" wheels don't actually have clearance for a 700mm diameter wheel at all.

A 622mm rim with a 28mm tyre would have a diameter of 678mm if tyre sizes were reliable, which they aren't.

So the 700 in 700C is completely meaningless. Why not just give the bead diameter of 622?

Well various sites all say that the letter is from an old French standard where it denoted the rim width. Possibly obsolete now, but still often there in the designation.

https://dev.azure.com/creditsafe/Da...est/96320?_a=files&path=/docker-pipelines.yml
https://bicycles.stackexchange.com/questions/16190/what-does-the-c-in-bicycle-tire-size-mean
https://www.cyclinguk.org/cyclists-library/components/wheels-tyres/tyre-sizes

 

[T4tomo]

Well various sites all say that the letter is from an old French standard where it denoted the rim tyre width / depth. Possibly obsolete now, but still often there in the designation.

i.e there were varying rim and tyre combos that added up to a nominal 700mm outer diameter.. 700A - 700D. (ish because the French are a bit ish). https://www.sheldonbrown.com/tire-sizing.html - scroll down to french sizes on this link

I agree with @Dogtrousers though, the 622 is a much more precise and useful dimension to have in the name, because most "700 C" road bikes end up with tyres leaving them well short of 700mm.

 

[Dogtrousers]

i.e there were varying rim and tyre combos that added up to a nominal 700mm outer diameter.. 700A - 700D. (ish because the French are a bit ish). https://www.sheldonbrown.com/tire-sizing.html - scroll down to french sizes on this link

I agree with @Dogtrousers though, the 622 is a much more precise and useful dimension to have in the name, because most "700 C" road bikes end up with tyres leaving them well short of 700mm.

Indeed. You can't use 700 to describe something of size 622 unless you account for the missing 78mm. That's where the size C tyre comes in. It would have a depth of 39mm if it existed. But it doesn't.