What Tyre Pressure Should My Car Be?

Most family cars run between 2.2 and 2.5 bar, which is 32 to 36 psi. But the right number for your car is printed on your car, and the place nearly everyone looks is the wrong one.

The number on the tyre is not the recommendation

The pressure moulded into the sidewall — often something like "MAX 51 PSI" — is the maximum the tyre can safely hold. It is a limit, not a target. Inflating to it gives you a hard ride, a narrow contact patch, and wear straight down the middle of the tread.

The figure you want is on a placard in the driver's door frame, sometimes in the fuel filler flap or the glovebox. It is set by the car manufacturer for that car's weight and suspension, not by the tyre manufacturer.

That placard is also where the unit problem starts. European and Japanese cars often print bar; the same car sold in the US prints psi; and plenty of placards give both, in a table that also splits front from rear and normal load from full load.

Bar	PSI	Typical use
2.0	29.0	Small city car, front
2.2	31.9	The most common family-car figure
2.5	36.3	Rear axle, or fully loaded
2.9	42.1	Van, or a car carrying maximum load

Convert your own with the bar to psi converter, or the other direction with psi to bar.

Check them cold, and know what "cold" means

Tyre pressure rises as the tyre warms up. Driving for twenty minutes will add roughly 0.2 bar (about 3 psi), and a hot motorway run can add more.

Every recommended pressure assumes a cold tyre — parked for at least three hours, or driven less than about two miles. If you check at a garage after a thirty-mile drive, you will read high and, if you "correct" it down, you will drive away genuinely under-inflated once the tyres cool.

Ambient temperature does the same thing more slowly. Pressure falls about 0.1 bar for every 10 °C drop, which is why the warning light tends to appear on the first cold morning of autumn on tyres nobody has touched.

What being wrong actually costs

Under-inflated is the dangerous direction. The tyre flexes more, the shoulders wear out while the centre stays fine, rolling resistance rises so fuel economy falls, and the sidewall builds heat. Sustained high-speed running on a soft tyre is how blowouts happen.

Over-inflated is mostly a comfort and grip problem. The contact patch shrinks toward the centre of the tread, so the middle wears out early, the ride gets harsh, and wet grip drops because there is less rubber on the road.

A tyre can be 20% low and look completely normal. Modern tyres have stiff sidewalls; the visual check that worked on 1970s cars does not work now. That is what TPMS is for, and it is worth knowing that most systems only warn at around 25% below target — by which point you have been driving on a soft tyre for a while.

Bikes are a different scale entirely

If you have arrived here from a bike pump, the numbers are much higher:

• Road bike: 6.9–8.3 bar (100–120 psi)
• Gravel: 3.4–4.8 bar (50–70 psi)
• Mountain bike: 1.4–2.1 bar (20–30 psi)
• Car: 2.2–2.5 bar (32–36 psi)

A mountain bike tyre and a car tyre run at roughly the same pressure for completely different reasons, and a road bike runs at three times either. This is why a single "correct" tyre pressure does not exist — it depends entirely on the load the tyre carries and the volume of air inside it.

The one-minute version

Find the placard in the door frame. Check the tyres cold. Use the loaded figure if the car is full. Add nothing "for safety" — the manufacturer already did.