Why Tyre Pressure Drops When It Gets Cold
A practical guide to tyre pressure cold weather for UK drivers, from the CarPal mobile tyre team.
Why pressure falls when it gets cold
Air contracts as it cools. The gas inside your tyre takes up less volume at 2°C than it did at 18°C, and since the tyre’s volume is fixed, the pressure drops.
The rough rule is 1 to 2 PSI lost for every 10°C fall in temperature. A tyre set correctly at 32 PSI on a mild October afternoon can easily read 28 PSI on a frosty November morning — enough to trigger a TPMS warning.
Do you need to add air?
Yes, but to the correct cold figure, not above it. The manufacturer’s pressure on your door sticker is a cold pressure, so top up to that number on a cold morning and you are correct.
What you should not do is over-inflate to compensate for winter. When the weather warms again you will be running over-pressure, with reduced grip and centre tread wear.
Why the light often appears on the first cold morning
Most drivers set their pressures in mild weather and do not touch them again. The first proper cold snap drops every tyre by several PSI at once, and any tyre that was already slightly low crosses the TPMS threshold.
If the light appears on a cold morning and all four tyres are a few PSI low, that is normal physics rather than four simultaneous punctures. If one tyre is much lower than the others, that is a puncture.
Winter checks worth doing
Check pressures more often through winter — every two to three weeks rather than monthly.
Check tread depth too. Wet and cold roads are exactly where worn tread costs you the most braking distance, and UK winter is mostly wet rather than snowy.
If you carry a spare, check that as well. A frozen morning at the roadside is the worst time to discover it is flat.
Frequently asked questions
Should I put more air in my tyres in winter?
Top them up to the normal cold pressure on your door sticker. Do not deliberately over-inflate for winter.
How much pressure do tyres lose in cold weather?
Roughly 1 to 2 PSI for every 10°C drop in temperature.
Why does my tyre pressure light come on when it's cold?
Cold air contracts, reducing pressure. If all four tyres are slightly low, it is temperature. If one is much lower, it is a puncture.
Will the pressure come back up when it warms?
Partly, yes. But if the tyre was genuinely low to start with, warming up only masks the problem. Set them correctly when cold.
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