Transport Canada says tire pressure changes by about 1 psi for every 5°C temperature change. Measure when tires are cold and inflate to the vehicle manufacturer’s specification—not automatically to the maximum number molded on the sidewall.
01 · TIRE MAINTENANCE
Cold air lowers the gauge reading
Air contracts as temperatures fall. Transport Canada notes that pressure changes by about 7 kPa, or 1 psi, for each 5°C change in temperature. A tire set correctly during a warm afternoon may read lower after an overnight cold snap.
This does not always mean the tire has a puncture, but repeated or uneven loss still needs investigation. Tires can also naturally lose pressure over time.
02 · TIRE MAINTENANCE
Check pressure when the tire is cold
For a useful reading, check before driving or after the vehicle has been stationary for at least three hours. Transport Canada also considers a tire cold if it has travelled no more than about 2 km.
Use the recommended cold pressure on the driver-door placard or in the owner’s manual for a passenger vehicle. The maximum pressure molded on a sidewall is not automatically the vehicle’s recommended setting.
03 · TIRE MAINTENANCE
Commercial vehicles require load-based care
Commercial tire pressure must support the actual load and application. Use the vehicle information and the tire manufacturer’s current load-and-inflation tables. Do not guess from tire size or copy another truck’s setting.
Check valve caps, inspect for penetrations and compare all tires on an axle. A consistent routine helps identify a slow leak before it becomes roadside downtime.
KEEP THIS HANDY
Quick checklist
- Use an accurate gauge
- Measure before driving
- Follow the vehicle placard or approved commercial load table
- Recheck after major temperature changes
- Inspect a tire that repeatedly loses pressure
- Remember the spare tire
Sources and further reading
Specifications and regulations can change. Follow the current vehicle, tire-manufacturer and government guidance for your situation.