Final answer:
Overinflated or underinflated tires can overheat, burst, or flex improperly. Over inflation increases internal pressure due to more molecule collisions, and underinflation causes tires to flex excessively. Optimal tire pressure is for cold tires, as temperature increases with use, raising pressure.
Step-by-step explanation:
When tires are either overinflated or underinflated, several issues can arise. If a tire is overinflated, the added pressure can cause more gas to fill the tire, leading to more frequent collisions of gas molecules, which increases the pressure inside. If continuing to inflate, the tire's walls will resist expansion, and the pressure will increase significantly. Consequently, the tires can overheat, possibly burst, or flex more than intended. These outcomes are further exacerbated when the car is driven since the flexing of the tires also raises their temperature, which in turn increases the pressure even more.
Most manufacturers specify the optimal tire pressure for cold tires because the pressure will rise naturally as the tire's temperature increases. Furthermore, no matter what causes an increase in the temperature of an already inflated tire, such as additional air pumping or exposure to sunlight, the resulting state of increased pressure would be the same, although the source of the heat may differ.