Car Tire Size / Tire accessories / Valve stems and caps
Valve stems and caps
The valve holds the air in; the cap keeps dirt and water out of it. Both are small, cheap and easy to forget, and a missing cap is the first thing to replace.
What to check before you buy
- Replace any missing cap: a dirty valve can leak.
- On many cars with TPMS, the sensor is part of the valve stem: buy caps and cores made for TPMS valves.
- Rubber snap-in stems age with the tire: they are usually replaced with new tires.
- Caps with a rubber seal inside keep water out better than plain ones.
How to use it
- Spray or brush soapy water on the valve, cap off.
- Watch for bubbles for a few seconds.
- Bubbles at the tip: tighten or replace the valve core with a valve core tool. Bubbles at the base: the stem needs a tire shop.
- Inflate to the door sticker pressure and put the cap back.