Of everything you can do for a car, tyre pressure is the cheapest, the quickest and the most neglected. Two minutes a month, with more effect on fuel, safety and tyre life than a great deal of expensive servicing.
The correct number is on a sticker inside the driver's door, not on the tyre sidewall. Check monthly, with the tyres cold, and do not forget the spare. An under-inflated tyre burns more fuel, wears at both shoulders, and builds heat until it fails at motorway speed.
Mistake one: reading the number off the tyre
Every tyre has a figure moulded into the sidewall next to MAX PRESSURE. Plenty of people use it. It is the wrong number.
That figure is the most the tyre can safely hold, not what your car needs.
The correct pressure is set by the car manufacturer, based on the vehicle's weight, how that weight is distributed, and its suspension. You will find it in one of three places:
- A sticker inside the driver's door frame — most common.
- Inside the fuel filler flap.
- The owner's manual.
It may differ front to rear, and there is often a higher figure listed for heavy loads or long trips.
Why it actually matters
Under-inflated
A soft tyre meets the road over a larger area, so resistance rises:
- Higher fuel consumption
- Wear at both shoulders while the centre stays fine
- Heat build-up — the most dangerous effect. The sidewalls flex more, temperature climbs, and at motorway speed that can end in a sudden blowout.
- Longer braking distance and slower response through corners
Over-inflated
- Wear down the centre only
- Less grip, because the contact patch shrinks
- A harsh ride and more sensitivity to potholes
- Greater risk of damage from hitting a kerb or a bump
The quick diagnostic: wear at both shoulders means chronic under-inflation. Wear down the middle means over-inflation. Wear on one side only is not a pressure problem at all — that is alignment or suspension.
Measure cold
A detail that invalidates the reading if ignored.
Driving heats the tyre, and warm air expands. After half an hour on the road the reading can be noticeably higher. If you measure then and bleed air off to reach the recommended figure, you have actually left the tyre under-inflated once it cools.
"Cold" means: before driving, after at least two hours parked, or after less than about two kilometres of slow driving.
Air contracts in the cold. With the first cold snap, warning lights come on in a lot of cars at once — that is not a fault, it is physics. Reset the pressure; do not just clear the light.
How to do it
- Know your number from the door sticker.
- Check cold, monthly and before long trips.
- Remove the valve cap and press the gauge on squarely until the hissing stops.
- Read it: add air if low, release if high.
- Re-check after adjusting.
- Do not forget the spare — the most neglected of the five, and usually discovered flat at exactly the wrong moment.
- Put the valve cap back; it keeps dirt and moisture out.
About the dashboard warning light
A pressure monitoring system is useful but not a substitute for checking, for two reasons:
- Many systems only warn after a large drop — as much as a quarter. By then the tyre has spent a long time in a damaging state.
- Some systems infer low pressure from differences in wheel rotation, so they do not notice all four tyres being equally low.
The light is an alarm for acute cases. The monthly check is what actually preserves the tyre.
Small things that extend tyre life
- Rotate the tyres as the manual specifies — wear is not even between front and rear.
- Check tread depth. Shallow tread cannot clear water, and the tyre starts to float on the surface in rain.
- Check age, not just mileage. Rubber hardens over the years even unused, showing as fine cracks in the sidewall.
- Look at the sidewalls for bulges. A bulge means internal structural damage and needs immediate replacement, not repair.
Two minutes a month, for lower fuel use, tyres that last longer and shorter braking distances. Very little maintenance pays like that.
Frequently asked questions
Where do I find the correct tyre pressure for my car?
Usually on a sticker inside the driver's door frame, sometimes inside the fuel filler flap or in the owner's manual. The number printed on the tyre sidewall is the maximum the tyre can take, not what the manufacturer recommends.
How often should I check?
About once a month, and before any long trip. A tyre loses some pressure naturally over time even without a puncture.
Should I measure hot or cold?
Cold — before driving, or after at least two hours parked. Driving heats the tyre and raises the pressure, giving a high reading that tempts you to let out air you actually need.
Why does pressure drop in winter?
Because air contracts when cold. Roughly every 10°C drop costs about 0.07 bar, which is why warning lights come on across whole car parks with the first cold snap.
Is nitrogen better than ordinary air?
It leaks slightly slower and is less affected by temperature, but the difference for everyday driving is small. Regular checks with ordinary air beat nitrogen you never check.
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