Tire pressure guide
What is the correct tire pressure?
The correct tire pressure is printed on a label inside the driver's door jamb (or sometimes the fuel filler cap) — not on the tire sidewall. That sidewall figure is the maximum cold inflation pressure, not the recommended operating pressure. Most passenger cars run 30–36 PSI (2.1–2.5 bar / 207–248 kPa) cold. Always check when the tires are cold (driven < 3 km).
Where to find the recommended pressure
- Door jamb sticker - inside the driver's door frame, on the B-pillar, or inside the door itself. This is the authoritative source.
- Owner's manual - lists pressure for all load conditions: driver only, full load, and trailer towing.
- Fuel filler cap - some models, especially older European cars, print the pressure here.
- NOT the tire sidewall - the number marked there, for example "MAX 51 PSI / 3.5 bar", is the maximum cold inflation pressure the tire casing can safely hold. It is not the manufacturer recommended operating pressure for your car.
Pressure units conversion
| Unit | Full name | Typical car range | Notes |
|---|---|---|---|
| PSI | Pounds per square inch | 30-36 PSI | Standard in USA, UK |
| bar | Bar | 2.1-2.5 bar | Standard in Europe |
| kPa | Kilopascal | 207-248 kPa | 1 bar = 100 kPa |
Quick conversion: 1 bar = 14.504 PSI = 100 kPa . So 2.3 bar = 33.4 PSI = 230 kPa.
Effects of incorrect pressure
| Condition | Tread wear | Fuel economy | Handling | Risk |
|---|---|---|---|---|
| Correct pressure | Even across full width | Optimal | Normal | None |
| Under-inflated (low) | Excessive wear on outer shoulders | Up to 3% worse per 10 PSI low | Sluggish steering; risk of aquaplaning | Overheating, sidewall failure, blowout |
| Over-inflated (high) | Excessive wear in centre tread | Slightly better rolling resistance | Harsh ride; reduced grip | Increased susceptibility to impact damage |
Temperature and pressure: the 1 PSI rule
Tire pressure changes approximately 1 PSI (0.07 bar) for every 10 °C change in ambient temperature. This is why tires that were correctly inflated in summer may trigger the TPMS warning in winter.
| Temperature change | Pressure change |
|---|---|
| +10 °C | +~1 PSI (+~0.07 bar) |
| -10 °C | -~1 PSI (-~0.07 bar) |
| Summer -> winter (-20 °C) | -~3 PSI (-~0.2 bar) |
Always re-check and adjust pressure at the start of each season and after any significant temperature swing of 10 °C or more.
TPMS - Tire Pressure Monitoring System
TPMS is mandatory on all new cars sold in the EU since 2014 and USA since 2008. The warning light, a cross-section of a tire with an exclamation mark, illuminates when any tire is 25% or more below the recommended cold pressure.
- Direct TPMS - a pressure sensor inside each wheel transmits real-time readings. Requires valve-cap battery replacement every 5-10 years.
- Indirect TPMS - uses ABS wheel-speed sensors to detect when an under-inflated tire rotates faster than the others. Cheaper but less accurate; must be reset after inflation or rotation.
- TPMS only warns at 25% low - a tire can be 10-15% low, several PSI, without triggering the light. Monthly manual checks with a gauge are still necessary.
How to check and inflate correctly
- Check when tires are cold: parked for at least 3 hours or driven less than 3 km.
- Remove the valve cap and press a calibrated tire gauge firmly onto the valve stem.
- Compare the reading to the door jamb sticker. Add air if low; release air by pressing the valve pin if high.
- Re-check after inflating; air compressors often add slightly too much.
- Replace the valve cap. Repeat for all four tires and the spare.
More tools
- Tire rotation guide
- Tire tread depth guide
- Tire age guide
- Speedometer error guide
- Tire size calculator
- Tire & wheel reference guides
Seasonal check
Planning a long summer drive?
Use the budget and running-cost tools before a trip, especially if the current tires are worn or the replacement size changes diameter.