Originally Posted by
Troul
the tube might physically reach a size large enough to bump the tire off its seated area.
Tubes impose almost zero resistance to stretching when subjected to pressure. They always stretch to fill the cavity within the rim and tire no matter what nominal size they are.
Like, if you take a "25mm" inner tube outside of a tire and start pumping it up, it will happily get
far larger than a 25mm tire even when its internal pressure is barely higher than that of the ambient air. The reason it doesn't get huge when it's inside of a 25mm tire is that it's being constrained by the tire.