Correct tyre pressure is one of the cheapest forms of car maintenance, yet it is often ignored. Under-inflated tyres wear faster, hurt fuel economy and can overheat, while over-inflation reduces grip and comfort.
This guide explains how to read tyre size codes, find the right pressure and understand how temperature and load change what you should use.
Reading Tyre Size Codes
A marking such as 205/55 R16 means the tyre is 205 mm wide, has a sidewall height equal to 55 percent of its width, is of radial construction and fits a 16-inch wheel. The load index and speed rating follow, for example 91V. Matching the correct size keeps your speedometer, gearing and clearance accurate.
Finding the Right Pressure
Never guess. Your car's correct cold pressure is printed on a sticker in the driver's door jamb, fuel filler flap or owner's manual. Typical passenger cars run around 30 to 36 PSI, but SUVs and vans differ. Pressures are quoted cold, so check before driving or after the tyres have cooled.
How Temperature and Load Change Pressure
Tyre pressure rises as tyres heat up on a long drive, sometimes by 3 to 5 PSI, which is normal. Do not bleed hot tyres down to the cold figure. For heavy loads or full occupancy, manufacturers often recommend higher rear pressures, so check the placard for the loaded condition.
When and How to Check
- Check pressures at least once every two weeks and before long trips
- Use a reliable gauge and check when tyres are cold
- Inspect tread depth and look for cracks, bulges or embedded objects
- Rotate tyres as recommended to even out wear
- Replace tyres when tread reaches the legal minimum of 1.6 mm
Frequently Asked Questions
Use the figure on your car's placard, usually found on the driver's door jamb or fuel flap. Typical passenger cars run about 30 to 36 PSI cold. Add a little for heavy loads if the manual recommends it, and always measure when tyres are cold.
Yes, air expands as it warms, so pressure rises during driving and in hot weather. This is normal, and you should not release air from hot tyres. Set pressures when tyres are cold, then let them rise naturally while driving.
Check at least every two weeks and before any long journey. Slow leaks, temperature swings and normal seepage all change pressure over time. Regular checks improve fuel economy, extend tyre life and keep you safer on the road.
Featured image: R. Henrik Nilsson (CC BY 4.0) License - via Source (Wikimedia Commons)
