I'm trying to understand wheels better and I googled Bead Seat Diameter and this image comes up a lot ...
There are two components that look to be the exact same with one flipped vertically.
Here is a picture of a 20 inch wheel for example:
What is considered the "bead"? Is it that little circle. A bead is normally just one small item on a necklace ( google ).
But in this case if it is that little circle, would the bead be something that creates a torroid and goes around the entire wheel?
From what I can tell the tire and the spokes are not depicted in the diagram, just the "metal" frame cross section.