Valve Stem
A self-contained rubber or metal tube on a wheel through which air is added or released from the tire.
A valve stem is a small tube protruding through the wheel rim that serves as the entry point for inflating and deflating a tire. It houses the tire valve core, which seals the air inside, and is fitted with a valve cap to protect the core from dirt, water, and debris.
Valve stems are made of flexible rubber (snap-in type) or solid metal (bolt-in type). Rubber valve stems can dry rot, crack, and leak over time due to weather exposure and high centrifugal forces at highway speeds. Metal stems use rubber grommets that can also degrade and leak.
In modern vehicles, the valve stem is often integrated with a TPMS sensor inside the wheel. It is standard safety practice to replace the valve stems (or the rubber seals on TPMS sensors) whenever new tires are installed to prevent slow leaks.