What occurs when drum brakes become overheated?

When drum brakes become overheated, the drums can experience excessive wear, leading to them becoming thin and potentially warping. This overheating can occur due to prolonged use, such as in situations that require continuous braking, like in mountainous driving or during heavy load conditions.

If the drums become too thin, they may not distribute heat as effectively and can lead to reduced braking efficiency. Over time, this weakening can cause the brakes to fail entirely, which poses a significant safety risk. In contrast, while the other options mention potential effects, they do not accurately represent what typically happens with heated drum brakes. For instance, brake pads melting is less common than the wearing of the drum itself, and hydraulic fluid boiling would more directly relate to disc brakes. Additionally, increased effectiveness of brake linings in overheated conditions does not occur; in fact, the braking performance can diminish as a result of overheating. Thus, focusing on the wearing out and thinning of the drums highlights the critical concern regarding brake maintenance and safety.