Why do you need to add air to your tires when it gets cold, but you don’t have to release air from your tires when it warms up?
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Recommended tire pressure ratings take a few different factors into account, including but not limited to fuel economy, towing and hauling capacity, and the health of the tire itself. Your tire’s performance and health is at greater risk when it’s pressure goes down versus when it goes up. An under inflated tire even at rest risks damage to the sidewall from the crushing force of the car’s weight. On the other hand, most tires have a recommended inflation pressure that is actually much lower than its burst pressure. If you check your tire sidewall on a typical stock sedan, it probably has a max rating of around 80 psi or so, but the vehicle user manual probably recommends only 35 to 40 psi. If your tire pressure goes up slightly in hot weather, it isn’t likely to put your tires at any sort of risk.
Technically you should, if you want to maintain the same PSI. After a long drive on a hot day, your air pressure will have increased, just as it decreases on a cold day
Sudden cold snaps will actually cause the rubber to contract. Air will leak out between the rim and bead when the tire deforms. This is more apparent with cheap tires. Source: I asked my best friends dad who has operated a tire store for 30+ years.
You do if you want to keep them at a specific pressure.
When we race motocross you want the tire at 12psi. In the morning when morning practice happens I will double check them at 12psi. By the time your races happen they climb to around 15psi as the day warms up. I’ve seen them as high as 17psi before bleeding them down.
Car and truck tires will be no different. Nitrogen filled tires may experience this less.
When it gets cold the air and rubber contracts slightly, so you will typically need to add more.
With a perfect system, you are correct in thinking that means when it warms up again the pressure will increase, and your tyres will end up overinflated.
In reality however, tyres will work over a range of usable pressures, and they will also always leak by a small amount.
This means that when it warms up your tyres will initially be over pressure, but this may not be hugely noticeable – they will still be within the acceptable range for your vehicle.
Over time the air will also leak a little, so at the start of the warmer seasons they will be over pressure, and they will slowly decrease over time to the ideal range, and possibly lower.
Even if you lived somewhere with a constant temperature year round, you will still need to top up your tyres occasionally just due to the slight leakage.
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