32 psi is about 220 kPa. Most cars built for metric markets have their placard printed in kPa; most tyre gauges and servo air pumps are calibrated in psi. Neither is wrong. They're just different units for the same pressure.
Pascal-based units (kPa) are the SI-derived standard used on new-car compliance plates in most of the world. Pounds per square inch (psi) survives because tyre gauges, especially cheap analogue ones, were standardised on psi decades ago and never fully switched over, even in countries that otherwise use metric units everywhere else.
| psi | kPa | bar |
|---|---|---|
| 28 | 193 | 1.93 |
| 30 | 207 | 2.07 |
| 32 | 221 | 2.21 |
| 34 | 234 | 2.34 |
| 36 | 248 | 2.48 |
| 40 | 276 | 2.76 |
This is the mistake worth avoiding. Moulded into every tyre's sidewall is a pressure figure. It is not a recommendation. It is the maximum the casing may hold, a structural ceiling, and it sits well above what most cars need. A standard passenger tyre reaches its full rated load around 35 psi. It is often branded 44 psi or higher.
Inflate to that and you have over-inflated the car. The contact patch shrinks. The ride hardens, wet braking suffers, and the centre of the tread wears out early. The US road safety regulator says it plainly: the correct pressure is not the number listed on the tyre.
The figure your car maker chose is a tuned compromise between grip, braking, ride, load capacity and wear for that specific vehicle. It lives on the placard.
Not always, but often. It comes down to weight over each axle. On most cars that means the front, because the engine and gearbox sit there. The heavier axle needs more pressure to hold the tyre at the right deflection.
There is a handling reason too. The front-to-rear split is tuned so the car pushes wide gently at the limit rather than snapping round. That is the safer way to run out of grip. Cars with weight spread evenly often specify the same figure at both ends.
Many placards carry a second, higher set of figures for a full load or towing. It usually rises more at the rear. If you are loading the car up, that is the column to read.
Placard pressures are cold pressures, and cold has a specific meaning. The car has been sitting three hours or more, or driven only a short distance slowly. Even the trip to the servo warms the tyres and lifts the reading. That is why a gauge at home reads lower than the same gauge after a drive.
The practical consequence is that you should never let air out of a warm tyre to bring it down to the placard figure. You will end up under-inflated once it cools.
Pressure also moves with the weather, roughly one psi for every ten degrees Fahrenheit, or about one psi per five and a half degrees Celsius. A tyre set correctly in February can read low on a cold morning in July without anything being wrong with it.
Some sites offer to calculate your tyre pressure from your vehicle's weight. We will not, and the reason is worth stating.
Doing it properly needs the load on each axle, not the kerb weight. It needs the exact load rating of the tyre fitted, and a load-and-inflation table from the relevant standards body. Those tables are public. But they exist for tyre fitters sizing a non-standard tyre, and every one says to use the placard for the original fitment.
Try it from kerb weight and you will land below the placard, because kerb weight understates the loaded axle. Under-inflation is what makes tyres overheat and fail. The placard already holds the answer the manufacturer's engineers reached.
Tyres lose pressure on their own, about one psi a month, as air permeates out through the rubber. That is normal. Losing noticeably more than that means a leak, not permeation.
And the dashboard warning light is not an early warning. Under the American standard most systems follow, it need not come on until a tyre is 25 per cent below placard. That is already deep into the range where damage happens. A gauge once a month catches what the light never will.