Tyre pressure: the right pressure in bar and psi for cars, trailers and bikes

The right tyre pressure is written in the car, not on the tyre. The manufacturer prints it on a sticker in the door frame or inside the fuel flap, and in the owner’s manual. Passenger cars usually run between 2 and 3 bar. Measure on cold tyres. Where the pressure is given in psi, as on many pumps and in US sources, 1 bar is 14.5 psi and 100 kPa.

Where do I find the right tyre pressure?

The recommended pressure is in the owner’s manual and almost always on a sticker inside the fuel flap or on the door pillar behind the driver’s or passenger’s door. The manufacturer usually gives two pressures: a lower one for normal driving and a higher one for a heavy load, high speeds or economy. Never run below the lowest figure given. The number on the tyre’s sidewall is the tyre’s maximum, not the car’s recommendation.

The sticker gives the pressure in bar, kPa or psi, sometimes all three. Convert with the tables below or with the psi to bar converter.

Psi to bar and kPa

1 psi is 0.0689 bar. A typical passenger car tyre at 32 to 36 psi is 2.2 to 2.5 bar.

Bar to psi and kPa

1 bar is 14.5 psi and exactly 100 kPa. Many stickers use kPa: 230 kPa is 2.3 bar.

More values from the converters for bar to psi, bar to kilopascal and kilopascal to bar.

Tyre pressure in winter

The pressure in a tyre falls as the air gets colder. A tyre filled to 2.5 bar indoors at 20 °C loses about 0.1 bar for every 10 degrees colder it gets outside, so at minus 10 it is down to about 2.1 bar. That is why the tyre pressure warning often comes on the first cold morning of autumn. Check the pressure when the cold arrives and when the winter tyres go on, and fill to the sticker’s value with cold tyres. If you have to measure on warm tyres, add about 0.3 bar, as Bilprovningen (the Swedish vehicle inspection company) advises.

Some manufacturers give a separate winter pressure in the manual. If there is none, the sticker applies all year.

Tyre pressure with a load or a trailer

With a fully loaded car, four passengers and luggage, or with a trailer, the higher pressure on the sticker applies. So the car’s own tyres go up when you hitch the trailer. The trailer’s tyres have their own recommended pressure, in the trailer’s manual or on a plate on the trailer, and it is often higher than the car’s. If there is no figure, ask the manufacturer or a tyre shop. Trailer tyres are easy to forget: check them before every longer trip.

Tyre pressure on a bicycle

Bicycle tyres carry the permitted range on the sidewall, usually in psi and sometimes in bar. Narrow road-bike tyres run at high pressure, wide mountain-bike and e-bike tyres at low pressure. Stay inside the range printed on the tyre. A floor pump shows psi, bar or both.

What happens with too little pressure?

The air carries the car, not the rubber. With too little pressure fuel consumption rises, the tyres wear faster and the car is harder to control in an evasive manoeuvre or hard braking. Bilprovningen states that 80 percent of the recommended pressure raises fuel consumption by 1 to 2 percent and cuts tyre life by 75 percent. NTF (the Swedish road safety association) and the Swedish tyre industry’s information council state that 30 percent too little pressure can halve tyre life, and that a difference of 0.5 bar or more between the tyres on one axle can make the car unstable. Too much pressure wears the centre of the tread and reduces grip.

How often should tyre pressure be checked?

At least once a month and always on cold tyres, meaning after the car has stood for a few hours. Stay within 10 percent of the recommended pressure, that is within 0.2 to 0.3 bar. Cars with tyre pressure monitoring, TPMS, warn when the pressure has dropped clearly, but the lamp does not replace the monthly check: a small loss does not trigger it yet still affects the tyre. When the lamp comes on, check and fill all four tyres, and reset the system as the manual describes if the car requires it.

Sources: Bilprovningen, advice on tyres (Swedish); NTF, tyre check list, appendix to a 2025 press release (Swedish); Däckbranschens informationsråd, correct tyre pressure (Swedish). The conversions between psi, bar and kPa use the site’s own factors. The temperature effect assumes the pressure in a sealed tyre follows the absolute temperature.