Valve stem

Valve stem

A valve stem is a self-contained valve which opens to admit gas to a chamber (such as air to inflate a tire), and is then automatically closed and kept sealed by the pressure in the chamber, or a spring, or both, to prevent the gas from escaping. They are most commonly used on automobile and bicycle wheels, but also for many other applications.

Schrader

Schrader valves (also called American valves) consist of a valve stem into which a poppet valve is threaded with a spring attached. They are used on virtually all automobile tires, and in the United States, on most wider rimmed bicycle tires. In addition to tires, Schrader valves of varying diameters are used in refrigeration and air conditioning systems, plumbing, fuel injection engines, suspension systems, and SCUBA regulators, allowing the user to remove and attach the hose while in use. Another use for Schrader valves is in the fuel injector rail of many automobiles, where it is used as a quick and easy point to check fuel pressure and to connect a cleaner injection device or cleaner cartridge.

Presta

Presta valves (also called Sclaverand valves or French valves) are normally only used on bicycles. The stem has a narrower diameter (nominally 6 mm) than the thinnest (nominally 8 mm) Schrader type, and so the bore of the hole in the rim through which the stem passes can be smaller. http://www.qtvalve.com/product/2/other-valve-component.html

valve stem