Bikes typically come with one of two types of valves. Schrader valves are typically called American valve and are abbreviated as AV, they are more common and exactly the same as those used on cars. They are found mostly on inexpensive bike models. Higher-end bicycle tires, however, are inflated with a Presta valve also known as French valve and abbreviated by FV, they are designed mostly for bikes. Here’s help on identifying them:
• Schrader Valve=American Valve=AV: Wider than a Presta and typically the same circumference top to bottom. Often wrapped in rubber when used on wheels. The outer wall is threaded to accept a cap or pump head. The pin in the center is a spring-loaded check valve that controls airflow in and out. Check valves are meant to allow airflow in only one direction; your Schrader-valve tube requires pressure on the inner pin to let air in.
• Presta Valve=Fren
ch Valve=FV: About half as wide as a Schrader and made entirely of metal. They come in a variety of stem sizes and longer stem sizes have become popular to fit Aero Wheels. They come with a top screw that when screwed will not let air out, to influx air into the bike tube you must unscrew counterclockwise the screw and usually push the screw a bit so that the check valve will allow input of air into the tube, once air start flowing into the tube the valve will seal automatically with air pressure. The valves are fully treaded so that a lock can be screwed into it fixing the tube into the rim, please don't over tighten the lock this may cause the valve to break apart of the inner tube.