A faulty tyre valve can leak air just like a puncture, and it's a common cause of a tyre that keeps going soft. Rubber valves perish and crack with age, and the small core inside can fail too. The fix is cheap, and the golden rule is to fit a fresh valve with every new tyre so it lasts as long as the tyre does.
How a valve leaks
The valve is the small stem you inflate the tyre through. Air can escape in two places: around the rubber base where it seals to the wheel (especially if the rubber has perished), or through the tiny spring-loaded valve core inside. Both cause a slow loss that mimics a slow puncture, which is why a leak isn't always the tyre itself.
Replace the valve with the tyre
A rubber valve has a limited life, much like the tyre. Because the valve is exposed when a new tyre is fitted, the sensible, standard practice is to replace it at the same time, for a tiny extra cost, so you don't fit a fresh tyre onto an ageing valve that may leak in a year or two. A new valve with every tyre is cheap insurance against a future slow leak.
TPMS sensor valves
Cars with direct TPMS have a pressure sensor built into the valve, which is more expensive than a plain rubber valve and has a battery that eventually dies. These need careful handling during a tyre change and sometimes a service kit (new seals) or replacement. If your car has direct TPMS, it's worth knowing the valves are part of the sensor, not just a plain stem.
Finding a valve leak
A leak from the valve is easy to confirm with the tyre off the wheel, using a water bath or leak spray to see exactly where the air escapes, see finding a slow puncture. That's the only reliable way to tell a valve leak from a tread puncture or a rim leak, which is why a proper inspection beats guessing.
We handle valves
We fit a new valve with every tyre and can diagnose and fix a leaking valve, including TPMS sensor valves, at your home or work across the UK. Book a check.
