Question

when a cold tire is inflated to a certain pressure and then is warmed up due to friction with the road, the pressure increases. This happens because the:

Answer 1

When the molecules are cold they don't move around very much and are more compact( as an idea if you were cold with a group of people you'd huddle for warmth). When heated they start to move rapidly and which expand. 

Answer 2

It is pressure temperature law. Gay Lussac's law.

Step-by-step explanation:

According to Gay lussac's law, the pressure of a gas increases with increase in temperature (keeping volume and moles constant).

This could be explained by the fact that when we increase the temperature of a gas sample, the molecules move faster and collide more randomly with the walls and thus increases the pressure.