What should be checked about the outer side wall?

The correct answer highlights the importance of checking for audible leaks in the outer side wall of a tire during a pre-trip inspection. When inspecting, it's crucial to ensure that there are no air leaks that could indicate damage or deterioration. An audible leak could lead to a loss of tire pressure, which not only affects the handling and performance of the vehicle but also poses a significant safety risk while driving. Maintaining proper air pressure is essential for optimal tire performance and longevity.

While checking for visible cracks, evenly worn tread, and the condition of the inner wall are all important aspects of tire maintenance, they do not carry the same immediate implications for safety as identifying audible leaks. If a tire is leaking air, it can quickly lead to a blowout or other tire-related issues that can compromise the safety of the vehicle and passengers. Therefore, actively listening for any audible leaks during your inspection is a critical step in ensuring the tire's integrity.