What is a sign that brake linings may be in poor condition?

The presence of grease or oil is a clear indicator that brake linings may be in poor condition. When grease or oil is found on the brake linings, it can diminish the friction necessary for proper braking. This contamination can result from various sources, such as leaking axle seals or engine oil leaks, and it compromises the effectiveness of the brakes, leading to longer stopping distances or even brake failure. Therefore, observing grease or oil on brake components necessitates immediate attention to ensure the vehicle's safety.

In contrast, minimum tread depth is related to tire safety, shininess is often a result of overheating which could indicate excessive wear, and no visible markings might pertain to the identification or condition of the pads but does not directly signify poor performance like grease or oil does.