[rotorwrench]

Tubes in the model T time frame were vulcanized natural rubber. After the war, the butyl rubber took over. Now that more tubes are being used for radial tires, they are using later technological formulas to take the heat better. Most are still chlorobutyl elatomers. Elastormers for the inner lining of tires and inner tubes may be using a halogenated isobutylene-co-paramethylstyrene polymer in some applications.

So far, I haven't seen any that use fluorosilicone polymers yet but who knows what is coming from Asia these days. When I go to Harbor Freight stores, I can smell some kind of nasty synthetic rubber smell in most of them.