What are the components of a valve stem?

Tires are made of several components that are necessary for the tires to function optimally and allow a vehicle to reach its potential. Tires are crucial for vehicle performance, feel, handling, and most importantly, safety. One key component within a tire is the valve stem.

The valve stem is the component responsible for inflation and deflation of a tire. They are essential for proper inflation levels, and when properly installed and functional, they will help to maintain tire safety and prolong the life of the tires.

What is a Valve Stem?

The valve stem is a small, tube that protrudes from the tire and is most often made of metal and rubber. The most common type of valve stem used in passenger vehicles is the Schrader valve. These are rubber valve stems with a metal tip that is threaded like a crew for the valve cap. These valve stems are also used on bicycles and motorcycles, though the construction materials may differ. Some high-end bicycles and other vehicles may incorporate the use of Presta valve stems, which are constructed completely of a metal alloy and are thinner in diameter. Valve stem construction also differs slightly based on the type of tire they will be used on. Valve stems for tubeless tires are considered a separate component from the tire itself, and they can become worn independently of a tire and may even need to be replaced by themselves.

However, if a valve stem is well manufactured and cared for, it may last longer than the tire associated with it. It is recommended that the valve stems are replaced when tires are replaced. For tires that require the use of inner tubes, valve stems will come as part of the inner tube. A valve stem will protrude directly from the body of the inner tube. The valve stem is placed through the appropriate opening in a vehicle's rim or wheel after one side of the tire has been mounted on the wheel and the inner tube has been slightly inflated within the tire.

How a Valve Stem Functions

Valve stems rely on a spring-loaded pin as well as the actual pressure within the tire in order to stop the air from running out of the tire. When you examine a valve stem, you can see the pin within the center of the stem. As a compressor head or pump head is placed on the valve, it depresses the pin, allowing air to enter or exit the valve stem, subsequently inflating a tire. Similarly, when the pin is depressed with no air pushing into the valve, the valve stem will release air. This makes the process of maintaining tire pressure a routine maintenance task that nearly everyone can do.

A tire gauge can be placed on the open valve stem to get a reading of PSI (pounds of pressure per square inch). If air needs to be added through the valve stem, a pump or a compressor with the appropriate attachment will do the trick. A compressor is recommended for the sake of efficiency. If pressure needs to be released, the reverse side of a standard tire gauge is equipped with a simple protrusion that is used for depressing the pressure pin within the valve stem.

In terms of caring for tires and valve stems, it is worth noting that valve stems can also be the culprit of a slow tire leak. A tire professional can inspect the tire for damages and leaks, or quickly find out if the valve stem is causing the problem. A leaky valve stem is a quick and inexpensive fix.

For the shaft which transmits motion from the outside to the inside of a valve, see Valve § Stem

Type of valve

Replacing a valve stem.

A valve stem is a self-contained valve that opens to admit gas to a chamber (such as air to inflate a tire),[1] and is then automatically closed and kept sealed by the pressure in the chamber, or a spring,[2][3] or both, to prevent the gas from escaping.[4]

There are many types of valves, and they are most commonly used on automobile, motorcycle, and bicycle tires, but also for many other applications. The most common type is the Schrader valve, but some road bicycles with skinny tires instead use the Presta valve.[5][6][7][8]

Schrader

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Schrader valve stem

Schrader valves consist of a valve stem into which a poppet valve 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 are used as a quick and easy point to check fuel pressure or connect an injector cleaner cartridge.[9][10][11][12][13][14][15][16]

Presta

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Presta valve stem

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.[17][18]

Dunlop (or Woods)

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Dunlop (or Woods) valve stem

Dunlop valves (also called Woods valves or English valves) were the dominating bicycle valves in the European region and many other countries. As of 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).[19] They can be pumped up with a Presta bicycle pump.[20]

Regina

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Regina Valve stem

The "Regina Valve" is very similar to the Presta and mostly used in Italy.[21][circular reference] The central threaded pin is so short that it does not protrude from the valve tube and therefore cannot be bent. In order to close the valve tightly, a small, loose nut is placed on this threaded rod with a diameter of only around 1.5 mm and screwed on by hand. A threaded rod is enough. By tightening the nut, the valve disc with the conical sealing body is pressed against the valve seat.

Rim drilling:⌀ 6.5 mm

Thread DIN 7756 • outside VG 6×32 •outside VG 5.2×24 at the upper end

Maximum pressure 15 bars.

Others

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Many other valves are used only in certain regions or for limited purposes.

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

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