What should the inside diameter of the brake drum not exceed?

The inside diameter of the brake drum is crucial for ensuring proper braking performance and safety. The maximum allowable increase in diameter is typically specified to maintain sufficient friction between the shoes and the drum. In this case, the brake drum’s inside diameter must not exceed 0.090 of the original drum size.

Allowing the diameter to increase beyond this threshold could lead to a reduction in braking efficiency, as the brake shoes would not be able to make effective contact with the drum's surface, resulting in decreased stopping power. This is critical for maintaining the vehicle's safety during operation. Additionally, exceeding the specified limit could also lead to uneven wear and potential failure of the braking system, which emphasizes the importance of regular inspections to ensure that all components are within safe operational limits.