Originally Posted by
woodcraft
By measuring?
The diagram shows the same tire, on the same rim, 23mm & 25mm being the same height.
Measure a few & see if you can duplicate that.
The diagram shows the outline of the amount of tire that is not hidden under the bead hook. Fatter tires on narrower rims are going to swallow up more of the sidewall making the tighter bend around the hook and under it. You aren't accounting for that.
If tires attached to the rim where the lines in the chart show, then you measuring method would make sense.