Abstract: A tire pressurizing system is provided for automatically pressurizing a pneumatic tire. The system employs centrifugal force to actuate a pump which is attached to the interior of the tire. Centrifugal force causes a pump actuating member to follow a different orbital path around a rotating tire from the path of the pump housing, which is attached to the tire. The difference is due to the flexing of the tire in the load bearing "footprint" area. The result is reciprocation of the actuating member, which in turn operates a pump. Piston and diaphragm pump embodiments are disclosed. An automatic pressure regulator is also provided.