Guide
How to check tire pressure correctly
Checking tire pressure is a two-minute job that most people do slightly wrong, in ways that make the reading meaningless. The method matters more than the gauge.
Start from the right number
Use the vehicle placard — the sticker in the driver’s door jamb, or the owner’s manual — not the number moulded into the tire sidewall. The sidewall figure is the tire’s maximum cold inflation pressure, not the pressure your car was designed around. A tire rated to 51 PSI on a car specified for 33 PSI should be run at 33.
The placard usually lists a different pressure for front and rear, and sometimes a higher figure for a fully loaded vehicle. That is not a mistake; it reflects how the weight is carried.
Check them cold
Tire pressure rises as the tire warms up, so a "correct" reading taken after a motorway drive can be several PSI above what the tire holds when it is cold. Measure before driving, or at least before the tires have done real work.
If you have to check warm, expect the number to be higher and do not bleed air out to hit the cold target — you will simply be under-inflated once the tire cools.
The routine
- Remove the valve cap and keep it somewhere it will not roll away.
- Press the gauge chuck squarely onto the valve stem until the hissing stops, then read.
- Take the value with the gauge still sealed; if you hear air escaping, the reading is being taken during a leak.
- Top up if low, bleed if high, and re-check after any adjustment.
- Refit the cap. It keeps dust and water out of the valve core.
Why all four, every time
Checking one tire tells you about that tire. Checking all four — plus the spare, if you carry one — is what reveals a slow leak, a sticking brake caliper, or a wheel that has been losing pressure since the last pothole. A single tire reading low while the others hold is the early warning that saves a wheel and a tire.
Keep a note of what you set and when. Two or three checks establish what normal looks like for your car, and anything that departs from it is worth investigating.
What TPMS does and does not do
Tire pressure monitoring is a warning system, not a measuring instrument. Depending on the vehicle it may only alert somewhere around a 25% deviation from the target, which is well past the point where fuel economy, wear and handling have already suffered. Use it to tell you that something is wrong; use a gauge to set the pressure.
Many systems also do not report which tire, and indirect systems that compare wheel speeds cannot see a slow leak that affects all four tires equally.
Frequently asked
How often should I check my tire pressure?
Once a month and before any long drive is the usual advice, plus any time the temperature drops sharply — pressure falls with temperature, so the first cold snap of the season is the moment most tires are suddenly under-inflated.
Should I use the tire sidewall or the door placard?
The door placard. The sidewall number is the tire’s maximum cold pressure, not the pressure your vehicle was designed to run.
The TPMS light came on but the tires look fine. Should I check?
Yes — a tire can be 25% under-inflated and look entirely normal from the outside. The light is telling you to measure, not to look.