Tyre pressure - measuring, converting, maintaining;
Correct tyre pressure is one of the most important parameters for safety and fuel economy. Below - how to measure properly, what the values in bar / psi / kPa mean, when to check, and what causes pressure loss.
What's the right pressure for my car
The manufacturer specifies recommended pressure for each size and load combination. You'll find it:
- On the sticker on the driver's door jamb (most accurate)
- Inside the fuel filler flap (on some brands)
- In the owner's manual
- Via the TrebamGume tool - enter make and model, get the factory recommendation
Typical values for passenger cars range between 2.0 and 2.6 bar (unladen) and 2.4 to 3.0 bar (fully loaded). Always measure when tyres are cold - at ambient temperature, not after driving.
bar, psi and kPa conversion
The same pressure is expressed in three units. 1 bar ≈ 14.504 psi ≈ 100 kPa.
| bar | psi | kPa | Note |
|---|---|---|---|
| 1.8 | 26 | 180 | below minimum - unsafe |
| 2.0 | 29 | 200 | small cars, unladen |
| 2.2 | 32 | 220 | mid-size, unladen |
| 2.4 | 35 | 240 | most cars, normal load |
| 2.6 | 38 | 260 | large cars / full load |
| 2.8 | 41 | 280 | SUVs, vans |
| 3.0 | 44 | 300 | vans, towing, heavy load |
| 3.5 | 51 | 350 | light truck |
Our tool shows pressure in all three units side-by-side - toggle on the model page.
Why correct pressure matters
Any deviation is a compromise. Neither under nor over is good:
Under-inflated (20% or more below)
- Higher rolling resistance → up to +5% fuel consumption
- Excess heat build-up → blowout risk at speed
- Shortened tyre life - uneven shoulder wear
- Slower steering response, longer braking distances
Over-inflated (10% or more above)
- Reduced grip - only the centre of the tread contacts the road
- Centre-strip wear - tyres last much less
- Harsher ride, less comfort
- Greater impact sensitivity - sidewall split risk over potholes
When and how to check
Minimum once a month + before long trips + every time before fully loading the vehicle.
Procedure (1 minute per tyre)
- Tyres must be cold (car hasn't driven in the last 2 hours, or less than 2 km).
- Unscrew the valve cap.
- Press the gauge firmly onto the valve. A brief hiss = poor seal, air leaking.
- Read the value. Below spec - add air. Above - bleed off (short press on the valve pin).
- Refit the cap.
Most modern cars have TPMS sensors that warn automatically when pressure drops. Don't rely on them alone - visual plus manual check is always better.
What causes pressure loss
- Ambient temperature
- Every -10°C drops pressure by about 0.1 bar. That's why TPMS often triggers in November - tyres aren't punctured, the air just contracted.
- Puncture (screw, glass, sharp object)
- Slow loss of 0.2–0.5 bar per day. Check visually - you'd be surprised what gets lodged in a tyre.
- Damaged valve
- Rubber ageing plus corrosion = leak. Valves should be replaced at every tyre swap.
- Deformed rim
- Pothole impact can bend the rim bead. Air escapes between rim and tyre bead. Rim must be removed and straightened.
- Porous tyre
- Very old tyres (9+ years) lose air through micro-pores in the compound. Replacement is the only fix.
Frequently asked questions
How often should I check tyre pressure?
Minimum once a month. Before long trips and before loading up - mandatory. Also after large temperature swings (summer → autumn).
Can I drive with 0.3 bar under the recommended?
To the nearest petrol station - yes. Beyond that - elevated risk. A 20%+ drop below spec causes heat build-up at speeds ≥90 km/h, significantly increasing blowout risk.
How much extra pressure for a heavy load?
Manufacturers usually give two values - "normal" and "fully loaded". For full load, add 0.2–0.4 bar to the normal spec. Exact value is on the door-jamb sticker.
Should I use nitrogen instead of air?
Not necessarily. Nitrogen loses pressure slightly slower (larger molecules), but the difference is about 0.1 bar per month. For everyday driving, regular compressed air is fine.
Why does pressure rise by itself in summer?
Air expands with temperature. A 10°C warm-up raises pressure by about 0.1 bar. Driving heats the tyre further - measure cold to avoid reading pressure plus thermal expansion.
Check the factory value for your car
TrebamGume shows the exact recommended pressure for each size on your vehicle - with bar/psi/kPa toggle.
Open TrebamGume