Wednesday, February 12, 2014
Tire Tube Stem Specs
There are three different kinds of tire tube stems: the Schrader, Presta and Dunlop valve stems. The Schrader valve is used on almost all automobile tires, the Presta is used on many road and mountain bikes and the Dunlop is a pneumatic valve used on bike tires in Japan and other countries that is somewhat out of date.
Schrader Valve Stems
A Schrader valve is most often made of brass with a threaded end. For tires, the stems are usually of a standard size, with an external thread of 7.7 millimeters and an internal thread of 5.30 millimeters. If you press the internal pin of the tire stem with a tire gauge, you can measure the internal pressure of the tire. A spring in the Schrader valve ensures that it stays closed.
Presta Valve Stems
Unlike Schrader valves, Presta valves have no spring, which makes them easier to pump. Presta valves are narrower than Schrader valves at 6 millimeters in diameter. A nut on the top of the valve allows air to flow in or out of the tire stem. After inflating the tire, you must screw the nut back on so air doesnt leak out.
Dunlop Valve Stems
The bottom of the Dunlop (or Woods) valve starts out at about the diameter of the Schrader valve and then decreases in diameter to about the size of the more narrow Presta valve (6 millimeters). You let air out of the Dunlop or valve by unscrewing the top ring on the valve stem.
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