If you’ve every gone to pump air into the tire of you car or bicycle and noticed that no air is released upon removing the plastic valve cap, then you’ve probably wondered why this part even exists at all. If it’s not the cap that holds the air in the tire, than why do we need to use one in the first place?
Well, this happens to be a purpose for these tiny, screw-on caps that protect the valve itself. The main purpose of the valve cap can vary based on the type of valve you’re dealing with. Where bicycles and cars are concerned, Schrader valves and Presta valves are most common. With the Schrader valve, the valve cap serves to prevent dirt and other unwanted particles from entering the valve seal. And with the Presta used valve, the valve cap was designed more to ensure safe shipping of the wheel.