Inflate tires to the recommended tire pressure when cold, like in the morning after the car has been sitting. Check your car’s owner’s manual for the recommended pressure, or inside the driver ...
This is commonly expressed as PSI, or pounds-per-square-inch. Tyre manufacturers have recommended tyre pressures, and car manufacturers actually have a placard (or tyre pressure chart) on all new cars ...
But it usually won’t rise by more than a few PSI. If your tire pressure is still significantly below the recommended level after driving, it’s unlikely to be just due to temperature changes ...