The Presta valve is a valve (commonly) found in high pressure "road" style bicycle tyres. It consists of three major components: the valve body; the valve stem; and the valve cap. In order to accommodate different rim wall depths, the valve body is available in two sizes; standard and extra long. The valve functions by winding the valve cap along the threaded valve stem, thus allowing for an open and a locked valve position. A Presta valve requires a different chuck on the bicycle tire pump than the bigger Schrader valve that is used on lower pressure bicycle tires and car or truck tires.
