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['CMV Parts and Maintenance']
['Brakes']
07/07/2026
Institute
Fleet Safety
CMV Parts and Maintenance
Transportation
What would you Do Answers
English
Brakes
Analysis
Focus Area
USA
Which of these vehicles are excepted?: Answers
Scenario 1 Answer: Yes. Trucks or truck tractors having three or more axles and manufactured before July 25, 1980, are not required to have brakes on the front wheels. These vehicles must meet the brake performance requirements in 393.52. Because this vehicle was manufactured in 1978, it is excepted from requiring brakes on all wheels.
Scenario 2 Answer: No. Any full trailer or four-wheel pole trailer (laden or unladen) with a gross weight of 3,000 pounds or less is not required to be equipped with brakes if the sum of the axle weights of the towed vehicle does not exceed 40 percent of the sum of the axle weights of the towing vehicle. Since the sum of this vehicle’s axle weights are well over 40 percent of the sum weight of the towing vehicle (sum of trailer axle weights is 3,000 pounds, the power unit is 3,400 pounds), this vehicle is not excepted.
Scenario 3 Answer: No. Brakes are not required on the steering axle of a three-axle dolly which is steered by a co-driver, but since this vehicle is being steered without a co-driver, the vehicle is not excepted from the brake rules.
cmv-parts-and-maintenance
CMV Parts and Maintenance
Which of these vehicles are excepted?: Answers
Scenario 1 Answer: Yes. Trucks or truck tractors having three or more axles and manufactured before July 25, 1980, are not required to have brakes on the front wheels. These vehicles must meet the brake performance requirements in 393.52. Because this vehicle was manufactured in 1978, it is excepted from requiring brakes on all wheels.
Scenario 2 Answer: No. Any full trailer or four-wheel pole trailer (laden or unladen) with a gross weight of 3,000 pounds or less is not required to be equipped with brakes if the sum of the axle weights of the towed vehicle does not exceed 40 percent of the sum of the axle weights of the towing vehicle. Since the sum of this vehicle’s axle weights are well over 40 percent of the sum weight of the towing vehicle (sum of trailer axle weights is 3,000 pounds, the power unit is 3,400 pounds), this vehicle is not excepted.
Scenario 3 Answer: No. Brakes are not required on the steering axle of a three-axle dolly which is steered by a co-driver, but since this vehicle is being steered without a co-driver, the vehicle is not excepted from the brake rules.
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Answer
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