TPMS: the sensors that watch your pressure for you

A Tire Pressure Monitoring System (TPMS) is a quiet second opinion. It watches your pressures while you drive and lights a warning the moment one drops far enough to matter — long before you'd feel it in the wheel. Understanding which kind your car has changes what you do when the light appears, and what happens when you change wheels.

What the light is telling you

The TPMS symbol is a cross-section of a tire with an exclamation mark — often described as a horseshoe with a '!' inside. A steady light means at least one tire is low. A light that blinks for a minute or two at startup and then stays on usually means the system itself has a fault, such as a dead sensor battery.

Direct vs indirect

There are two ways to measure pressure, and they behave very differently in daily use.

When the light comes on

1. Don't panic, but don't ignore it

   Ease off, avoid hard braking or cornering, and find somewhere safe to check. A warning is usually a slow leak, not a blowout — but treat a sudden one as a possible flat.

2. Check all four with a gauge

   TPMS tells you something is low, not by how much. Measure each tire and inflate back to the door-placard figure.

3. Reset if needed

   Indirect systems need a reset after inflating so they relearn the 'correct' baseline. Direct systems clear themselves within a short drive once pressures are right.

Sensors and a new set of wheels

This is the part that surprises people at purchase. If your car uses direct TPMS, a second set of wheels (your winter set, for example) needs its own sensors fitted into the valves and paired to the car — otherwise the light stays on all season. Indirect systems carry nothing in the wheel, so a new set just needs a reset. When you're choosing wheels with us, factor this in: it's a small, known cost, not a surprise.