Smokin Joe said:
The diameter of a 700c wheel is actually 622mm. I think the 700 refers to the approximate diameter when a tyre is fitted, and it is the standard size roadbike wheel.
I agree you're right, it just doesn't make a lot of sense, not today at any rate
622 is the wheel diameter (to the tyre bead seat, not rim-to-rim), so a 700 wheel including tyre would need a tyre (700 - 622) = 78, /2 as it's twice the tyre 'height' => 39
So it would be a '700' wheel with a 39mm tyre.
Perhaps that was a standard tyre size in 1910 or whenever they invented this system, but today we're all running racers round on 700/23 (= 688) or tourers on 700/28 or 32 (= 678 or 686)