That does make the presumption that the tread on a tire cannot stretch
That was my mistake. I was thinking of the extreme case of Top Fuel dragsters. They use non-steel belted tires inflated to around 6psi and the centrifugal force greatly increases the tire O/D at high revs, acting rather like a CVT.
Compare stationary to rotating:
Definately a change in diameter.
Sorry it's completely off-topic, I'll shut up now.