A manual tire pump will inflate a bicycle tire, automobile tire, utility trailer tire or even a basketball or air mattress with the right fittings for air transfer. Most pumps, whether manual or electric, work on the same basic principle. The main differences are in cost, portability, ease of use and effort expended.
Theory
The basic principle of how a tire pump works has to do with valve systems and compression of air. Depending on the strength and sealing capacity of the material holding air, a high volume of air can be held in a small space. A steel canister of compressed air (as in a typical "fix-a-flat" aerosol can) will inflate an auto tire of much larger volume using a lower PSI (Pounds per Square Inch). That aerosol can was filled with an electric pump that pulled atmospheric air from the surroundings at the normal pressure of 14.7 PSI and compressed it using a system of valves to as high as 100 PSI, so that it can inflate a tire with six times the volume of the canister.
Mechanics
In a manual tire pump, whether hand or foot operated, air is brought into a vacuum-sealed chamber as a piston pulls outside air into the chamber. A valve opening to the outside is opened to let that air in and the valve opening to the tire is closed. On the down stroke, the valve to the outside air is closed and the valve leading to a hose of air going to the tire is opened. The act of pushing that piston down compresses the air, forces it into the tire and raises the pressure so the tire inflates and holds weight. The higher the pressure, the more weight can be sustained. The harder the inflated bicycle tire is, the less rolling resistance for pedaling.
Types
Whether a hand or foot operated pump is used, the theory of low pressured air intake and higher pressured air expulsion is the same. Electric pumps use the same principle, even if driven by a power supply in an automobile like a cigarette lighter. The larger the hand or foot pump, the more air can be transferred into the tire and the faster it can be inflated. More force and therefore effort must be used for such high pressure pumps. Easier to operate pumps will expel less air under lower pressure and will take longer to inflate a tire. In a hand pump, both up and down motions are needed with a push and pull to operate the pump, while a foot pump usually has a spring mechanism to automatically open the valve, which is then depressed by stepping on the activator for the piston chamber.
Options
Because of innovations in manual and compressed air containers, many options are open to the biker, driver or hobbyist. Compact hand air pumps that have a fill hose that disappears into the air chamber when mounted on a bicycle can be almost indistinguishable from the frame of the bike. Such a small apparatus will have a significantly smaller air compression chamber and may take a long time to fill even a thin racing bicycle tire.
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