Tire Pressure kPa to psi

Tyre pressure: kPa, psi and fuel efficiency

The units line up like this: 1 bar = 14.5 psi = 100 kPa, which puts 1 psi at roughly 6.895 kPa. Check the reference values on the door-jamb sticker. Popular cars sit around 30-32 psi (210-220 kPa), an SUV runs about 35 psi (240 kPa), and a light truck can need 80+ psi (550+ kPa) on the rear axle. Run a tyre 20% under-inflated and rolling resistance climbs, your fuel consumption goes up 3-5%, and the sidewall flexes and heats more than it should. That is a real blowout risk at highway speed. Always measure cold, because the air heats up after a drive and will read 4-6 psi higher than reality. Altitude bumps things up too, roughly 0.5 psi for every 1,000 m you climb. The correct cold pressure is in your car manual and on the Inmetro listing.

Applications: fuel economy, safety and maintenance

You will see this come up in fuel-economy math (at gas stations and in apps like Drivvo), in Inmetro safety inspections, in how caminhoneiros manage their fleets, and in the routine monthly calibration every manufacturer asks for. Modern cars carry TPMS (Tire Pressure Monitoring System), which the EU has required since 2014. In Brazil it stays optional, though it shows up often on imports.

FAQ

Should I inflate hot or cold? Cold, every time. That means before you drive, or after the car has sat for at least 3 hours. A hot reading can run 4-6 psi high, which leaves you under-inflated once things cool down.

Does nitrogen really help? A little. It leaks out a bit slower and reacts less to temperature swings. But for normal street driving, that edge is tiny next to just calibrating your tyres every month.

What is the +2 psi rule for highway? When you are going to hold high speed for a while or run fully loaded, put 2-4 psi over what the manual says. The extra pressure offsets the heat buildup and the sidewall flex.