If you're a casual cyclist who goes on the occasional weekend ride around the neighborhood, you probably don't think too much about what type of valve stem you have on your tires. In fact, you may not be aware that there are different types at all. If you've ever bought a bike online from overseas, however, you may encounter an unusual looking stem that requires an entirely different pump than you're used to.
Woods Valve
The Woods valve is still widely used in Europe and Asia but rarely seen in the United States. It is also known as the Dunlop valve in honor of its creator, John Boyd Dunlop, who invented the pneumatic tire and built a tire empire in the process. The valve itself is a low-tech affair held in place by pressure and spit. Newer versions are sometimes spring loaded. You can use a standard Presta pump to fill tires with a Woods valve, but you'll need to get it set just right. The valves can be finicky.
Schrader Valve
Most consumer bikes in the United States use Schrader valves. These are the same type that you are probably familiar with from topping off your car tire. They are uniform in shape and simple in design. Covered with a threaded, plastic cap screwed on to a 7.7 mm top, the Schrader valve uses a pressurized core to hold air in the tube. When the core is depressed by the pump, a pathway opens for air to flow into the tire.
Presta Valve
Presta valves are the design of choice for professional cyclists on competition bikes. They are lightweight and more aerodynamic than Schrader valves, and, because they're thinner, they more easily fit through drill holes in the narrow rims found on competition road bikes. The valve is capped with a captive nut, meaning it can be unscrewed but not completely removed. When the nut is tightly secured, it prevents air leakage in high-pressure tires better than a typical Schrader valve. You need a Presta pump to fill a tire with a Presta valve. You can find one at any quality bike shop.
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