Well lets say that you are in a dessert hotel, and when you get up in the early morning, its 30 American Degrees outside (Fahrenheit for you foreigners). You check your tires and make sure you put them at 42 PSI before you take off...per manual specs.
By the middle of the day, you and in the kingdom-come dessert road which is now at 90 degree ambiance; your tire probably much hotter than that. You check your pressure at the truck stop and its 54 PSI. You need to take some air out due to the expansion of the air inside the tire due to the heat.
All this can be done without a calculator, nor the theoretical applications of Boyles' Charles' nor Amonton's Principles...can't it? BTW, I just taught a Physics course at a Community College in my village, so I know it can be done.