Underinflated tyres lengthen your stopping distance, make the steering vague, wear out at the shoulders, run hot and use more fuel. Overinflated tyres reduce grip and wear out in the middle. Neither announces itself until something goes wrong, and a tyre can look perfectly normal while being significantly low.
A monthly check with a decent gauge takes five minutes and is one of the highest-value things you can do for your own safety.
Find the right pressure first
The number you need is not the one moulded into the tyre sidewall. That figure is the tyre’s maximum, not your car’s recommended pressure.
The correct figures come from a placard fitted to the car, usually in one of these places:
- The driver’s door frame or door pillar, visible with the door open
- Inside the fuel filler flap
- In the glovebox
- In the owner’s manual
The placard usually lists two sets of figures: normal running, and a higher set for a fully loaded car. Many also list a separate figure for the spare, which is often much higher.
Cold tyres, always
Driving warms the air inside a tyre and raises its pressure, so a reading taken after a drive will be higher than the truth. “Cold” means the car has been parked for at least three hours, or driven less than a couple of kilometres.
This is the practical problem with filling at a fuel station: if you drove several kilometres to get there, your tyres are already warm. If that is your only option, check them there consistently so at least you are comparing like with like, and take a cold reading at home when you can.
Checking and adjusting
- Unscrew the valve cap and keep it somewhere safe. A lost cap lets grit into the valve.
- Press the gauge squarely onto the valve stem. A brief hiss as you seat it is normal; a continuous hiss means it is not square.
- Read the figure and compare it with the placard.
- If it is low, add air in short bursts and re-check. Most airlines over-deliver if you hold them on.
- If it is high on a genuinely cold tyre, press the small pin in the valve centre briefly to release air, then re-check.
- Refit the cap.
- Repeat for all four tyres — and the spare.
Do not forget the spare
A spare that has been sitting in the boot for three years is very often flat, and a flat spare is no spare at all. Check it whenever you check the others. If your car carries a space-saver, note that it usually needs a considerably higher pressure and has a speed limit marked on it.
While you are down there
A pressure check is a good moment to look at the tyre itself:
- Tread depth. Tyres have small raised bars set into the grooves; when the tread wears level with them, the tyre is at its legal limit. Many markets, including India, set that limit at 1.6 mm — confirm the rule where you drive.
- Uneven wear. Wear concentrated at both shoulders suggests chronic underinflation; wear down the centre suggests overinflation; wear on one edge only usually points to alignment and is worth having checked.
- Damage. Cuts, bulges in the sidewall, or objects embedded in the tread. A sidewall bulge means the tyre’s internal structure has failed — do not drive on it.
- Age. The sidewall carries a four-digit code in an oval showing the week and year of manufacture. Rubber hardens with age even on a tyre with plenty of tread left.
If your car has a pressure monitor
A tyre pressure monitoring system warns you when a tyre falls below a threshold. It is a warning device, not a substitute for a gauge — by the time it triggers, the tyre is already well below where it should be.
After adjusting pressures, some systems need resetting through the car’s menu or a button so they relearn the new baseline. Your manual explains the procedure for your car. If the warning symbol stays on after a correct reset and correct pressures, have the sensors checked.
Your manual has the final word
Recommended pressures, loaded-car figures, spare tyre pressure and the monitor reset procedure are all specific to your car. Where this guide and your owner’s manual or door placard disagree, follow the car.
