Commercial Driver License (CDL) Class B Practice Test

What are two primary causes of tire fires?

1. Overheating and ice on the road

2. Under inflated tires and duals that touch

3. Old tires and high speeds

4. Worn brake pads and fuel leaks

The correct answer is: Under inflated tires and duals that touch

Under-inflated tires and duals that touch are indeed significant contributors to tire fires. When tires are under-inflated, they generate excessive heat due to increased friction with the road surface and greater flexing as they roll. This heat buildup can lead to the tire's materials breaking down, which can ignite, especially if other factors contribute to a higher risk of fire. Additionally, when dual tires touch, it creates friction between the two surfaces, which can further increase heat. If either condition persists, the chance of a tire fire occurring rises considerably due to the combination of excessive heat and the potential for structural failure in the tire. In contrast, while old tires can present risks, the age of a tire does not directly lead to overheating in the same way that improper inflation does. High speeds can exacerbate tire problems but are not primary causes of tire fires like the lack of proper inflation and physical contact between dual tires. Similarly, worn brake pads and fuel leaks affect vehicle operation and safety but are not direct factors linked specifically to tire fires.