Tyre pressure is one of the most-overlooked maintenance items and one of the most consequential. Underinflated tyres reduce fuel economy, wear unevenly, run hot (with risk of catastrophic failure at highway speed), and increase stopping distances. Overinflated tyres reduce grip, give a harsh ride, and wear in the centre. Checking and adjusting pressure correctly takes 5 minutes and pays back immediately.
Where to Find the Correct Pressure
The correct pressure for your specific vehicle is on the tyre placard, which is usually located on the driver’s door jamb, inside the fuel filler door, or in the glovebox. The placard lists the recommended pressure for normal load and full load, plus any spare tyre pressure. Note that the pressure listed is the cold pressure – measured before driving, when tyres are at ambient temperature.
Do not use the pressure listed on the tyre sidewall – that is the maximum safe pressure for the tyre, not the recommended pressure for your vehicle. Always follow the vehicle placard.
Cold vs Hot Pressure
Tyre pressure rises as the tyres heat up from driving – typically 4 to 7 psi (28 to 48 kPa) increase after 30 minutes of motorway driving on a warm day. The placard pressure is the cold pressure (before driving). If you check pressure when tyres are warm, expect them to read 4 to 7 psi above the placard figure – that is normal. Never let air out of warm tyres to bring them down to the placard pressure; you will end up underinflated when they cool down.
Frequency of Checking
Check pressure at least monthly, or before any long trip. Tyres lose roughly 1 to 2 psi per month through normal permeation through the rubber, plus more in cold weather (pressure drops about 1 psi for every 10 degrees Celsius). A tyre that was perfect in summer can be 5 psi low by winter just from temperature change.
Heavy Loads and Towing
The placard usually lists a higher pressure for full load conditions – typically 4 to 8 psi above the normal pressure. Use this when carrying heavy loads, when fully loaded for a holiday trip, or when towing. Failing to increase pressure for heavy loads causes overheating, premature wear, and risk of tyre failure. Once you return to normal load, drop back to the standard pressure.
TPMS (Tyre Pressure Monitoring System)
Modern vehicles have TPMS that warns when pressure drops significantly below specification – typically 25% below the placard figure. The dashboard warning is set off only at this point, so by the time it lights up, you have been driving on a significantly underinflated tyre for some time. Manual checks are still important; do not rely on TPMS to catch slow leaks or seasonal pressure drops in time.
Some TPMS systems are direct (using sensors in each wheel) and others are indirect (calculating tyre pressure from wheel speed differences via the ABS sensors). Direct systems are more accurate but require sensors to be activated/programmed when wheels are swapped or sensors replaced.
Spare Tyre – Often Forgotten
Always check the spare tyre too. A flat spare is useless when you need it. Space-saver spares typically need much higher pressure than regular tyres – check the placard. Most TPMS systems do not monitor the spare, so manual checking every 6 months is essential.
For specific tyre pressure specifications and TPMS reset procedures, MechanicMate offers PDF workshop manuals for over 960 models at mechanicmate.net/shop.
— MechanicMate . Questions or a second opinion? [email protected].