Tire Pressure & Temperature Calculator
Air shrinks when it's cold. See what your tires will actually read when the weather turns — and why the first cold snap is blowout season for trailers.
Cold pressures — measure before driving. Example preset: an ST trailer tire aired to 65 PSI in a 75°F summer garage, checked on a 30°F morning.
That's 8% under your set pressure. Underinflation builds heat — the number-one killer of trailer tires — and wears shoulders fast. Top up to the placard or sidewall pressure at the colder temperature.
Your 65 PSI (set at 75°F) across the seasons
| Ambient | 90°F | 70°F | 50°F | 30°F | 10°F |
|---|---|---|---|---|---|
| Cold PSI | 66.8 | 64.4 | 62.0 | 59.5 | 57.1 |
Tires taking a beating?
Heat-worn trailer tires don't announce themselves. Check the tread and the date code, then let us sort the replacement.
Common questions
How much pressure does a tire lose in cold weather?
About 2% of its pressure for every 10°F drop — roughly 1 PSI on a 35-psi passenger tire, but closer to 1.3–1.5 PSI on a 65-psi trailer tire and 2 PSI on a 100-psi commercial tire. The percentage rule (real gas law) is what this calculator uses.
Why did my TPMS light come on the first cold morning?
Pressures set in warm weather drop with the season: air set at 75°F reads noticeably lower at 30°F. Nothing is leaking — but the tire really is underinflated now, so top it up at the colder temperature.
What pressure should trailer tires run?
Unless the trailer manufacturer specifies otherwise, ST trailer tires run at the maximum pressure molded on the sidewall — their load capacity is rated at that pressure, and underinflation is the leading cause of heat-related trailer tire failures.
Should I check pressure hot or cold?
Cold — before driving, or after the vehicle has sat for 3+ hours. Driving heats the air and raises the reading, which masks underinflation.