[header] How to inflate bike tires [title] A schrader valve is also called an american valve, or a car valve. [step] The valve stem is surrounded by a threaded valve core; to press down on the stem, you need to use a tool like a pen cap or your thumbnail. Schrader valves are typically wider in diameter and shorter than presta or woods valves. 
They're usually found on cars, less expensive bikes and mountain bikes. To open a schrader valve, simply unscrew the rubber cap at the top.