During a brake drum inspection, what indicates that the drum might be defective?

A brake drum inspection is critical for assessing the condition and safety of a vehicle's braking system. The presence of cracks reaching the outer edge of the brake drum indicates a potential defect because it compromises the structural integrity of the drum. Cracks can lead to failure during vehicle operation, especially under the stress of braking. A crack that extends to the edge suggests that the drum may not effectively handle the forces during braking, increasing the risk of malfunction. This can result in decreased braking performance, potential brake failure, or even dangerous situations while driving.

In contrast, a clean friction surface is actually a positive indicator, suggesting that the drum is functioning effectively without significant wear debris or scoring. The inner diameter being smaller than the maximum specification could indicate wear and potential issues; however, it is not as immediate a sign of defect as visible cracks are. Finally, if the drum is securely fastened, it reflects proper installation rather than a defect in the drum itself. Each of these factors plays a role in the overall assessment of brake drum condition, but cracks are the most serious concern.