What is a critical aspect to check when inspecting brake pads?

When inspecting brake pads, checking the thickness is crucial for ensuring they are within safe limits. Brake pads have a finite lifespan, and as they wear down, their thickness decreases. If the pads become too thin, they may not provide adequate stopping power, which can lead to brake failure and pose a serious safety risk. Maintaining appropriate thickness allows the braking system to function effectively, ensuring that the vehicle can stop safely and promptly.

While the other options may be relevant in certain contexts, they do not carry the same weight as thickness in terms of immediate and critical safety. The color of the pads, for instance, may indicate wear but is not a definitive or standard measure of safety. The type of material used is important for performance but does not directly affect the wear state of the pads at any given time. Dust or debris on the pads can indicate other maintenance issues but does not directly address the essential aspect of ensuring that the pads are thick enough for safe operation.