Disclosed herein are systems, methods, and computer-readable storage media for gravity-driven pumps, gravity-driven power generators that power electric pumps, as well as various supporting concepts, mechanisms, and approaches. As a tire rotates around an axle, the pull of gravity varies for a given point on the tire. While gravity is always pulling ‘down’, the force relative to a fixed point on the tire changes. Gravity-driven pumps exploit these changes in gravitational force to do work. Automatic, gravity-driven pumps can be used to inflate tires to offset the natural gas leakage of modern tires, and can maintain tire pressure and inflation within a desired or optimal range. As different conditions are met, pump parameters are determined which can adjust the pumps. Such conditions include driving patterns, load, and temperature, and resulting adjustments include turning on and off pumps, varying stroke length, and varying the number of strokes required.