CDL Combination Vehicles TestCombination Vehicle Air BrakesMedium
A driver is inspecting the brake drums and linings on a combination vehicle. Which of the following conditions indicates a serious problem that requires immediate repair?
- ASmall amounts of dust are present on the brake components.
- BBrake linings appear shiny or glazed.
- CBrake linings are worn to less than 1/4 inch thickness.
- DBrake drums show slight discoloration from heat.
Show answer & explanationAnswer & explanation
Correct answer: C. Brake linings are worn to less than 1/4 inch thickness.
Brake linings worn to less than 1/4 inch thickness (or to the wear indicator if present) are considered critically worn and must be replaced immediately to ensure effective braking and prevent metal-to-metal contact.
Why the other options are wrong
- A. Small amounts of dust are a normal byproduct of brake lining wear and not an immediate cause for concern.
- B. Shiny or glazed linings can reduce braking effectiveness but are generally not as critical an issue as severely worn linings, though they should be addressed.
- D. Slight discoloration from heat is normal for brake drums under heavy use and doesn't necessarily indicate a serious problem.
Brake Lining Wear Limit
The minimum allowable thickness of brake linings before requiring replacement, typically 1/4 inch for most vehicles.
- Critical safety inspection point.
- Prevents metal-to-metal braking.
- Ensures effective stopping power.
Memory trick: Thin linings mean immediate stopping of your journey.