Tyre pressure: the right numbers and how to check
There is no universal correct pressure: the right numbers are printed on your car, not on the tyre. Here is where to find them, how to check in five minutes, and what running wrong does to grip, fuel and tyre life.
Where the right numbers live
On the placard inside the driver’s door frame, inside the fuel flap, or in the handbook, listed front and rear, often with a second set for full load. The number moulded on the tyre sidewall is its maximum, never your target.
How to check in five minutes
Check cold, before driving or after a couple of miles at most, because pressure rises with heat. Unscrew the valve cap, press the gauge on square, read, top up in short bursts, and recheck. Do all four and the spare, then refit the caps.
How often
Once a month and before any long or fully loaded trip. Tyres lose pressure slowly all the time, and a visual glance cannot spot the difference until it is well below spec.
What running the wrong pressure actually costs
Underinflation is the expensive one: the tyre flexes and overheats, the shoulders wear fast, fuel consumption rises, and braking and cornering get vague. Badly underinflated tyres can fail outright at speed. Overinflation wears the centre strip, makes the ride harsh and shrinks the contact patch in the wet. A tyre naturally loses a small amount of pressure every month, which is why monthly checks matter even with no puncture.
Loaded up for a trip? Most cars list a second, higher set of pressures for full load: use it, then drop back after.
About that pressure warning light
The TPMS light means a tyre has dropped well below spec, so treat it as a check-now signal, not a suggestion. Top up to the placard figure and see whether it returns: a light that comes back within days means a slow puncture that needs looking at. After any top-up or tyre change, drive a few minutes so the system relearns, and reset it if your handbook says so.
Common questions
Is the pressure on the tyre sidewall the one I should use?
No. The sidewall figure is the maximum the tyre can hold, not a recommendation. Always inflate to the car maker’s placard figure, which is set for your car’s weight and handling.
Should front and rear tyres have the same pressure?
Often they differ: engines, drivetrains and load sit differently over each axle. Use the placard’s separate front and rear figures rather than averaging them.
Does temperature really change tyre pressure?
Yes, roughly 1 to 2 percent per 10 degrees Celsius. A tyre set in summer can sit meaningfully low by winter, which is why a cold snap so often lights the TPMS warning across a whole car park.
Can I drive with the pressure light on?
Briefly and gently, to the nearest air line. The light means a tyre is well under spec, and grip, braking and the tyre itself degrade the longer it runs low. If the tyre is visibly flat, stop and change or call assistance instead.
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