A system is used with a pneumatic tire mounted on a wheel rim to keep the pneumatic tire from becoming underinflated. The first system includes a plurality of pumps attached circumferentially to the wheel rim, each pump having pump parameters, and a control valve for controlling inlet air into a tire cavity of the pneumatic tire. The control valve has valve parameters. The system predicts system performance under various configurations and conditions through use of the pump parameters and the valve parameters.

A system is used with a pneumatic tire mounted on a wheel rim to keep the pneumatic tire from becoming underinflated. The first system includes a plurality of pumps attached circumferentially to the wheel rim, each pump having pump parameters, and a control valve for controlling inlet air into a tire cavity of the pneumatic tire. The control valve has valve parameters. The system predicts system performance under various configurations and conditions through use of the pump parameters and the valve parameters.

A tire air filling device according to one embodiment includes: a cylinder; a weight which has an air flow hole and which receives a centrifugal force to move and cause air to be supplied to an inside of a tire; a first sealing member; a first spring; a first support portion; and a backflow prevention valve. The backflow prevention valve includes a slide member that slides in the air flow hole in an axial direction, a second spring that biases the slide member to a side opposite the tire, a second support portion that supports an end portion of the second spring in the axial direction; and a second sealing member interposed between an inner surface of the air flow hole and the slide member. The slide member, the second spring, and the second support portion are disposed inside the weight.

In variants, a two-stage pump can include a piston and a cylinder cooperatively defining a first stage in front of the piston fluidly connected to a second stage behind the piston, wherein a forward stroke of the piston pressurizes working fluid in the first stage and forces pressurized working fluid into the second stage, and a backward stroke of the piston further pressurizes working fluid in the second stage and exhausts pressurized working fluid out a pump exhaust.

In variants, a two-stage pump can include a piston and a cylinder cooperatively defining a first stage in front of the piston fluidly connected to a second stage behind the piston, wherein a forward stroke of the piston pressurizes working fluid in the first stage and forces pressurized working fluid into the second stage, and a backward stroke of the piston further pressurizes working fluid in the second stage and exhausts pressurized working fluid out a pump exhaust.