A valve stem is a self-contained

valve A valve is a device or natural object that regulates, directs or controls the flow of a fluid (gases, liquids, fluidized solids, or slurries) by opening, closing, or partially obstructing various passageways. Valves are technically fittings ...

which opens to admit gas to a chamber (such as air to inflate a

tire A tire (American English) or tyre (British English) is a ring-shaped component that surrounds a Rim (wheel), wheel's rim to transfer a vehicle's load from the axle through the wheel to the ground and to provide Traction (engineering), t ...

), and is then automatically closed and kept sealed by the

pressure Pressure (symbol: ''p'' or ''P'') is the force applied perpendicular to the surface of an object per unit area over which that force is distributed. Gauge pressure (also spelled ''gage'' pressure)The preferred spelling varies by country and e ...

in the chamber, or a

spring Spring(s) may refer to: Common uses * Spring (season) Spring, also known as springtime, is one of the four temperate seasons, succeeding winter and preceding summer. There are various technical definitions of spring, but local usage of ...

, or both, to prevent the gas from escaping. They are most commonly used on

automobile A car or automobile is a motor vehicle with Wheel, wheels. Most definitions of ''cars'' say that they run primarily on roads, Car seat, seat one to eight people, have four wheels, and mainly transport private transport#Personal transport, pe ...

motorcycle A motorcycle (motorbike, bike, or trike (if three-wheeled)) is a two or three-wheeled motor vehicle steered by a handlebar. Motorcycle design varies greatly to suit a range of different purposes: long-distance travel, commuting, cruising ...

, and

bicycle tire A bicycle tire is a tire that fits on the wheel of a bicycle or similar vehicle. These tires may also be used on tricycles, wheelchairs, and handcycles, frequently for racing. Bicycle tires provide an important source of suspension, generate ...

s, but also for many other applications.

Schrader

Schrader valves consist of a valve stem into which a

poppet valve A poppet valve (also called mushroom valve) is a valve typically used to control the timing and quantity of gas or vapor flow into an engine. It consists of a hole or open-ended chamber, usually round or oval in cross-section, and a plug, usual ...

is threaded with a spring attached. They are used on virtually all automobile and motorbike tires, and on wider rimmed bicycle tires. In addition to tires, Schrader valves of varying diameters are used in refrigeration and air conditioning systems, plumbing, engine fuel injection, suspension systems, and SCUBA regulators, allowing the user to remove and attach a hose while in use. The Schrader valves in the fuel injector rail of many automobiles is used as a quick and easy point to check fuel pressure or connect an injector 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. Has a locknut that needs to be opened to inflate/deflate.

Dunlop (or Woods)

Dunlop valves (also called Woods valves or English valves) were the dominating bicycle valve in the European region and many other countries. Today (2021), Presta valves are just as common in these regions. Dunlop valves are still widely used especially on low to medium priced bicycles (city and trekking bikes). They can be pumped up with a Presta

bicycle pump A bicycle pump is a type of positive-displacement air pump specifically designed for inflating bicycle tires. It has a connection or adapter for use with one or both of the two most common types of valves used on bicycles, Schrader or Pre ...

.Sheldon Brown's Bicycle Glossary
/ref>

Others

Many other valves exist that are used only in certain regions or for limited purposes. For example, the "Regina Valve" is a valve very much similar to the Presta and mostly being used in Italy. Invisible tire valves are different in design from traditional tire valves. An inflator stem is not used; instead, a removable cap on a valve stem embedded in the tire rim is fitted, with only the cap visible. When inflating the tire, the cap is first removed, typically with a coin, and then a "portable" dedicated inflator stem is screwed onto the valve stem. Through the inflator the tire is inflated as usual.

References

External links

by Sheldon Brown
common types of valves used for bicyclesadvantages Of tire monitoring valve cap
{{Bike equipment Tires Valves Bicycle parts