Does cold weather change your tire pressure?
It does, in a direction you can predict and by an amount most riders overestimate. The numbers on this page are the gas law, not our engine.
Baró has no temperature input at all, and this page says what that costs you and what to do about it.
Yes, and less than you think
Air in a sealed tire follows a law you can check: cool it and the pressure falls, warm it and it rises. Nothing leaks, nothing is wrong with the tire — the same air is simply pushing less hard.
The reason the effect is smaller than most riders expect is that your gauge does not read the pressure in the tire. It reads the difference between the tire and the air around it, and the law applies to the total. Work it through properly and a 20°C garage to a 10°C morning costs a 38 psi gravel tire about 1.8 psi, not the three or four people assume.
What a cold morning actually costs
Pumped at 20°C indoors, then ridden at the temperature down the side. Gravel is a 38 psi tire, road is 80 psi.
That is worth correcting. Wheel the bike outside for ten minutes and pump it there, and the whole problem goes away with no arithmetic.
Change from a 20°C pump, sea level · psi
| Riding at | 38 psi gravel | 80 psi road |
|---|---|---|
| 20°C | 0.0 | 0.0 |
| 10°C | −1.8 | −3.2 |
| 0°C | −3.6 | −6.5 |
| -5°C | −4.5 | −8.1 |
Read the two columns against each other and you have the part worth knowing: the colder it gets the more you lose, but a road tire loses roughly 1.8× what a gravel tire does for the same ten degrees. The effect scales with how much air is in there, so high pressures move most.
Baró does not know the temperature
There is no temperature input in this calculator and no temperature term in the engine behind it. Not a simplification — it genuinely is not modelled. Everything on this page is the gas law, which belongs to nobody and which you can check against any physics text.
We could add a term. We have not, because the honest version of it needs the temperature where you pumped AND the temperature where you are riding, and a calculator that asks for both is a calculator most people abandon. The workaround below costs a rider nothing and needs no input at all, which is a better trade than a field nobody fills in.
This is a gap, and it is in your number
If you pump in a warm room and ride in the cold, the number this site gives you will be a little high when you set it and a little low by the time you are riding. Nothing on this page is compensating for that automatically. That is what the next section is for.
Pump where you ride, not where it is warm
The whole problem disappears if the air is already at riding temperature when you set it. Wheel the bike outside, give it ten minutes, then pump. That is the entire fix, it costs nothing, and it is more accurate than any correction either of us could calculate.
If you cannot — a shared hallway, a winter morning, a pump that lives indoors — add roughly 1.8 psi for every ten degrees between the room and the road on a gravel tire, and about 3.2 psi on a road tire. Then ride it and rate it, and the app will take it from there on your own terms.
Cold ground is not the same as cold air
Falling temperature does two things at once and only one of them is in the gas law. The air loses pressure, which is this page. The rubber also gets stiffer and the ground gets harder, and frozen ruts behave nothing like the same trail in September.
That second half is a surface question, not a temperature one, and it is the half the calculator does handle: tell it the ground is rougher and it will come down for you. The surface layer is where that happens, and it is a much larger effect than the psi you lost to the cold.