There are three main types of valve stems: Schrader, Presta and the less popular Woods valve. Each comes with a different set of pros and cons. The Woods valve and the Presta valve can be inflated with the same size inflation pump, while the Schrader valve requires a different size. Schrader valves benefit from their use in the automotive industry -- just about every petrol station in the country has a pump for Schrader valves.
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Presta valves, also known as French valves or Sclaverland valves, are commonly used in road bicycles because they hold higher air pressures better than other valves. The air pressure inside the tire holds the inner valve closed, and a captive nut on the outer body must be closed to seal the air inside the tube. The locking nut must be unlocked in order to inflate or deflate the tube. The valve body, however, cannot be removed, and flat repair fluids cannot be injected without temporarily breaking through the tube.
The Presta valve has a 6mm diameter and can be used in wheels drilled for Schrader valves as long as an adaptor is used to fill in the extra space. The narrower diameter results in a stronger rim.
By far the most popular valve type, the Schrader valve is used in just about every automobile tire on the planet. These valves are held shut by a compression spring that pulls a rubberised plunger against the end of a brass tube, and the standard diameter of the Schrader valve is 8mm. The standard threading for this type of valve is 32 threads per inch, according to bicycle expert Sheldon Brown. Modern Schrader valves have been developed with a sensor to transmit air pressure data to a tire pressure monitoring system (TMPS), a feature first introduced by Porsche in 1986.
The cap is a more integral feature of Schrader valves than Presta valves. The pin that opens the valve sits flush against the top of the valve stem, which if not covered can accumulate dirt.
Woods and Regina Valves
Woods valves were developed in England and can be inflated using a Presta valve pump. Also known as Dunlop valves, they have a ring that screws the smaller part onto the base of the stem. They are held shut with the pressure inside the tube, much like the Presta valve, and the valve body is more accessible than other types.
Regina valves are very similar looking to Presta valves, and are almost exclusively used in Italy. They can be inflated using Presta tire pumps.
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