DOT Vehicle Maintenance & Repair Standards 2 — Questions and Answers
Question 1: Under FMCSA regulations, what is the minimum acceptable brake lining thickness for a drum brake on a steering axle?
- 1/16 inch
- 1/8 inch (Correct answer)
- 4/32 inch
- 3/16 inch
Correct answer: 1/8 inch
FMCSA regulations require a minimum brake lining thickness of 1/8 inch (4.8 mm) on steering axle drum brakes before the vehicle is placed out of service.
Question 2: A DOT inspector finds a hydraulic brake line with a visible crack but no active leakage. How should this be cited?
- No citation required until leakage is observed
- Out-of-service condition (Correct answer)
- Driver warning only
- Schedule repair within 30 days
Correct answer: Out-of-service condition
A cracked brake line is an out-of-service condition under 49 CFR 393.45, as it presents an imminent risk of brake failure regardless of current leakage status.
Question 3: Which federal standard governs the performance requirements for commercial motor vehicle brakes?
- 49 CFR Part 571 FMVSS 121 (Correct answer)
- 49 CFR Part 393 Subpart C
- 49 CFR Part 396.3
- 49 CFR Part 325
Correct answer: 49 CFR Part 571 FMVSS 121
Federal Motor Vehicle Safety Standard 121 (49 CFR Part 571.121) establishes the air brake performance requirements for new commercial vehicles.
Question 4: During a roadside inspection, a tire on a non-steering axle measures 2/32 inch tread depth. What is the correct action?
- Issue advisory and allow travel
- Out-of-service the vehicle (Correct answer)
- Require repair within 24 hours
- No action required
Correct answer: Out-of-service the vehicle
A tread depth of 2/32 inch or less on any non-steering axle tire is an out-of-service condition per CVSA standards.
Question 5: What is the maximum permissible free play in a manual slack adjuster on a 15-inch brake drum?
- 1 inch
- 1.5 inches (Correct answer)
- 2 inches
- 2.5 inches
Correct answer: 1.5 inches
For a 15-inch brake drum, the maximum allowable pushrod travel (free play) for a manual slack adjuster is 1.5 inches per CVSA out-of-service criteria.
Question 6: A CMV's steering gear box has visible cracks in its housing. The inspector should:
- Note it in the report for follow-up
- Place the vehicle out of service immediately (Correct answer)
- Allow travel if steering effort feels normal
- Require repair within 72 hours
Correct answer: Place the vehicle out of service immediately
A cracked steering gear box housing is an immediate out-of-service condition because structural failure could cause total loss of steering control.
Question 7: Under 49 CFR 396.3, motor carriers are required to systematically inspect, repair, and maintain all vehicles. Which record must be kept for each vehicle?
- Daily trip log only
- Driver qualification file
- Periodic inspection report for at least 14 months (Correct answer)
- Vehicle purchase invoice
Correct answer: Periodic inspection report for at least 14 months
49 CFR 396.3 requires motor carriers to retain the most recent periodic inspection report and the previous inspection report, effectively covering at least 14 months.
DOT Vehicle Maintenance & Repair Standards 2
Under FMCSA regulations, what is the minimum acceptable brake lining thickness for a drum brake on a steering axle?