So what you are saying Leon is that 24” tyres will fit on the same size rims that also take 26”?

The rims are about the same diameter.

In the olden days, tyres were labelled with their (nominal) rolling diameter. So (very roughly), a 24 x 2 tyre has a rolling diameter of 24" and fits on a rim of diameter 24 - (2 x 2") = 20", and a 26 x 3 tyre is 26" overall, and fits on a rim 26 - (2 x 3") = 20". (In practice the rim sizes are usually about 20 1/2" and 21".)

However a 26 x 2 tyre fits on a rim about 26 - (2 x 2") = 22". Historically, 26 x 2 1/4 was an oversize tyre for a 26 x 2, so it also goes on a 22" rim. 26 x 2 1/2 was another oversize, still on 22" rim.

Of course a 28 x 3 tyre also goes on a 22" rim, since 28 - (2 x 3") = 22".

There were attempts to introduce standards for beaded edge rims in the early 1920s, but in practice rim and trye sizes varied somewhat from maker to maker.

Make sense?

Leon