Originally Posted by
alpineboard
The distance length of the circumference does not change when loaded, it stays the same, as when unloaded.
When going from an unloaded state to a loaded state, the radius changes at this contact point area, but the vital idea
to keep in mind is that one complete revolution equals one circumference distance length of forward travel distance.
Opinions welcome please thank you.
If the wheel was completely rigid, the wheel would have this radius (the patch radius). It's the circumference of this imaginary wheel that the roll-out is measuring.
If the radius changes (due to different loads, mostly), the circumference changes.
With a higher load, the bicycle moves a shorter distance with each full rotation of the wheel.
The "circumference" (the path of the outer edge) of the tire doesn't change but it doesn't matter what that number is (as long as the patch radius is the same).