Originally Posted by
Sy Reene
Maybe that's how you measure it, but it's pretty meaningless in reality.. and how do you get a caliper or ruler down where the bead is to take that measurement anyway?
Any measurement involving wheels and tires are difficult to make. All official measurements of wheel rims are referring to the bead seat diameter (BSD) which is an internal measurement. It's not the bottom of the rim, its not the top of the rim, its in the middle. A 700c wheel rim has a BSD of 622mm. Good luck in trying to measure it.
Bicycle tires are 100% profile so a tire that measures 25mm wide is going to be 25mm higher than the bead + the thickness of the tread.