What is the Schrader valve

The Schrader valve (also called American valve is a type of pneumatic tire valve used on virtually every motor vehicle in the world today. The Schrader company, for which it was named, was founded in 1844 by August Schrader. The original Schrader valve design was invented in 1891, and patented in the United States in 1893.

The Schrader valve consists of a valve stem into which a valve core is threaded, and is used on virtually all automobile tires and motorcycle tires and most wider rimmed bicycle tires. The valve core is a poppet valve assisted by a spring.

Uses

In addition to tube and tubeless tires, Schrader valves of varying diameters are used on many refrigeration and air conditioning systems to allow servicing, including recharging with refrigerant; by plumbers conducting leak-down pressure tests on pipe installations; as a bleeding and test port on the fuel rail of some fuel injected engines; on bicycle air shock absorbers to allow adjustment of air pressure according to the rider's weight; and in the buoyancy compensator (BC) inflators of SCUBA systems where the ability to easily disconnect an air hose (even underwater) without the loss of tank air is critical. Schrader valves are also widely used in high-pressure hydraulic systems on aircraft.[citation needed] Many domestic fire extinguishers use an internal valve identical to a Schrader valve, but with a lever on top to enable quick release of the pressurized content.

Valve

A Schrader valve consists of an externally threaded hollow cylindrical metal tube, typically of nickel plated brass. In the center of the exterior end is a metal pin pointing along the axis of the valve stem; the pin's end is approximately flush with the end of the valve body.

All Schrader valves used on tires have threads and bodies of a single standard size at the exterior end, so caps and tools generally are universal for the valves on all common applications. The core of the valve can be removed or tightened with a tool.

Industrial Schrader valves are available in different diameters and valve core variants and are used in refrigeration, propane, and a variety of other uses.

A new development is Schrader valve stems with integrated transmitters for tire pressure monitoring systems (TPMS).

Cap

A valve cap is important on a Schrader valve because if one is not fitted, dirt and water can enter the inside of the valve stem, potentially jamming it or contaminating the sealing surfaces and causing a leak.

Metal, and some hard plastic valve caps have a rubber-washer seal (or a synthetic-rubber-washer seal) inside to help make a hermetic seal (airtight seal). The cap helps prevent air from escaping from a slightly leaking valve. In addition, the rubber washer prevents the cap from loosening and falling off due to vibrations and hence being lost, by acting as a cushion between the cap and the valve stem and in this way damping the vibrations, though most caps are a softer plastic making the need for a separate seal unnecessary.