Tim Streater wrote:

Andy Burns wrote:

So are saying the circumference remains constant, hence the rpm
remains constant, hence iTPMS cannot work?

The steel cords may stretch a little, but that's all. Without that, the
circumference *must* stay constant.

The steel belts aren't parallel to the circumference, they're on a low
angle diagonally, so they can bunch-up or space-out with the distortion
of the tyre as it revolves, so the change in circumference can be more
than just you'd get by stretching them, though it still only needs to be
small to be measurable.