CDL Air Brakes TestInspecting Air Brake SystemsMedium
A driver is inspecting the brake linings on a commercial vehicle with air brakes. What is the minimum acceptable thickness for brake linings on most heavy-duty vehicles?
- A1/8 inch
- B1/2 inch
- C3/8 inch
- D1/4 inch
Show answer & explanationAnswer & explanation
Correct answer: D. 1/4 inch
Federal regulations and most state laws require brake linings to be at least 1/4 inch thick on most heavy-duty vehicles. Some manufacturers may specify slightly different minimums, but 1/4 inch is the general accepted minimum. If the lining is worn thinner or contaminated with oil/grease, it must be replaced.
Why the other options are wrong
- A. 1/8 inch is too thin; the lining would be severely worn and unsafe.
- B. 1/2 inch is thicker than new linings; this is incorrect.
- C. 3/8 inch is typically the thickness of new linings, not the minimum.
Brake Lining Minimum Thickness
The smallest allowable thickness for a brake lining before it must be replaced to ensure safe and effective braking.
- Typically 1/4 inch for heavy-duty vehicles.
- Check for oil/grease contamination as well.
- Worn linings reduce braking power and can damage drums.
Memory trick: Quarter inch is the line, below that, your brakes aren't fine!