What is the maximum allowance for resurfacing a drum's braking surface?

The maximum allowance for resurfacing a drum's braking surface is important for maintaining safety and performance. Resurfacing can help extend the lifespan of the drum while ensuring effective braking performance.

Allowing up to 0.080 inches beyond the original diameter compensates for wear and helps maintain the drum's structural integrity. This allowance provides a reasonable amount of material to be removed without compromising the drum's effectiveness. Under this allowance, drums can still function efficiently while accommodating additional wear that can occur over time.

Furthermore, allowing 0.040 inches under the maximum diameter needed for additional wear ensures that the drum does not become too thin, thereby preventing the risk of failure during operation. By setting both allowances, this approach balances the need to remove worn material and maintain sufficient braking capability.

In essence, both allowances work together to create a guideline that preserves the performance and safety of the braking system, making the combination of these two allowances the correct answer.