Valve stems are the small tubes on your rims that allow you to re-inflate a tire after pressure is lost or after a tire is repaired or replaced.
Each valve stem, quite logically, holds a valve. The valve allows pressurized air — or nitrogen, if used — to flow into the tire without then escaping. It also enables you to lower tire pressure by depressing the valve and allowing some air to escape.
You’re probably thinking, “My old valve stems don’t leak, so I’ll just leave them on. What could go wrong?”
What Can Go Wrong With Old Valve Stems?
Plenty: As they age more, valve stems could develop leaks, even if there are none now, resulting in premature wear, flats, or damage to a Tire Pressure Monitoring System.
Valve stems are not intended to last forever. UV rays from the sun, salt and age can result in cracks. Improperly replaced wheel covers may cut them. Scuffs against curbs or rocks also can damage them. Even a slow leak means that unless you repeatedly fill the leaky tire, pressure will dip, affecting handling and possibly leading to a tire-ruining flat. Low pressure can also result in uneven, premature wear, which will cost you money when you have to replace a tire much earlier than if it had been properly inflated.
Replace Valve Stems:
- If you see visible damage when you flex the stem.
- Whenever you have a tire replaced.
Are all Valve Stems the Same?
Not all valve stems are the same. A rim with TPMS must use a compatible stem — either a snap-in rubber stem that’s compatible or in some cases, an aluminum stem. Your repair or tire shop mechanic will know.
Stems come in different lengths. If your car has wheel covers, make sure the garage mounting your new or used tires uses a valve stem long enough to allow checking pressure with a gauge and refilling the tire without removing the wheel cover. Valve stem extenders are inexpensive, but they don’t always seal properly. Improperly sealed valve stems can allow loss of pressure and contamination by water and dirt, leading to valve corrosion and failure.
Metal stems usually are not necessary, but they do have a cosmetic value. Some owners of high-end aftermarket rims have metal stems installed to better match the look of the wheels. Blue metal high-pressure stems are advisable for high-performance track diving in which speeds top 130 mph. It’s important to remember that if you do use an aluminum stem, the valve must be compatible — nickel plated, not brass. Using an improper brass valve with an aluminum stem would cause a galvanic reaction that leads to corrosion and eventual valve failure.
What About Nitrogen and Nitrofill?
Nitrogen inflation requires better-sealing metal valve caps. These silver-colored caps also frequently carry a green top surface, often marked N or N2 for nitrogen. Avoid bringing up tire pressure in a nitrogen-filled tire by pumping in air. It’s safe, but doing so will destroy the advantages of nitrogen, including lower pressure loss. Nitrogen inflation costs about $10 per tire, so you want to make sure valve stems and valves on nitrogen-filled tires are sound.