As soon as the pressure in these Goodyear tires (which don’t have an official retail price yet) gets too low, they know it. An internal pressure regulator opens to allow air to flow into a pumping tube, and as the wheel turns, the flattened part helps squeeze air from the tube through an inlet valve into the tire. Once the air pressure hits an optimal level, the regulator closes—all without the driver’s realizing anything was wrong.