Short Answer
Typically tire pressure varies 2 to 3 psi (0.14 to 0.21 bar) per 10°F (5.5°C). The change in pressure is because air expands when it is warmed and contracts when it is cooled.
Detailed Explanation
Why pressure changes
Air expands when it warms and contracts when it cools. Since a tire is a sealed system, any change in air temperature directly affects the internal pressure.
When outside temperature increases:
-
The air inside the tire warms up
-
Internal pressure increases
When outside temperature decreases:
-
The air inside the tire cools down
-
Internal pressure decreases
Example
If a tire is set to 100 PSI (6.9 bar) at 70°F (21°C), and the ambient temperature drops to 40°F (4°C), the tire pressure may naturally decrease by approximately 6 to 9 PSI (0.41 to 0.62 bar) due to the change in temperature.
Why this matters
Seasonal temperature changes can cause pressure to drop below the configured Cold Inflation Pressure.
This may result in:
-
Low pressure alerts
-
Increased tire wear
-
Reduced fuel efficiency
-
Increased rolling resistance
When to check tire pressure
The proper time to check the Cold Inflation Pressure is when the tire is cold. A tire is considered cold when it has been parked for at least 3 hours and has not been exposed to direct sunlight.