HEAVY TRUCK BRAKES MICHIGAN
MECHANIC ACTUAL EXAM 2026
QUESTIONS AND DETAILED RATIONALES
ALREADY PASSED
⩥ What legislation mandates every required standard of a highway truck
air brake system?. Answer: FMVSS 121
⩥ If a truck is FMVSS 121 compliant, which of the following air
reservoirs must be incorporated into the air brake circuit?. Answer:
Supply, primary and secondary tanks
⩥ In a truck air brake system which sub circuit is primarily responsible
for actuating front axle service brakes when the system is functioning
normally?. Answer: Secondary circuit
⩥ When a FMVSS 121 compliant tractor trailer combination is moving
down the highway at a speed of 50 mph, which circuit must be charged
with air?. Answer: Hold off circuit
⩥ What best describes the functions of a tractor protection valve?.
Answer: Pressure protects the tractor air supply in the event of loss of
pressure in a trailer
, Routes trailer supply air and service application signal to the trailer
pneumatic circuits
Blocks service signal air to the trailer until trailer air supply is activated
⩥ If you have yo make an adjustment to air system cut off pressure
where should the adjustment be made?. Answer: The governor
⩥ How is the relay section of an FMVSS 121 compliant duel circuit foot
valve activated when the air brake is functioning properly?. Answer:
Pneumatically
⩥ What is the function of a quick release gladhand when used?. Answer:
Speeds service brake release timing
⩥ What best accounts for brake feel in an air brake system?. Answer:
Resistance of application pressure versus for pressure
⩥ What is the potential energy of an air brake system?. Answer:
Compressed air
⩥ When a tractor spring brake assembly is charged with air on both its
service and hold off chambers what results is known as?. Answer:
Compounding
MECHANIC ACTUAL EXAM 2026
QUESTIONS AND DETAILED RATIONALES
ALREADY PASSED
⩥ What legislation mandates every required standard of a highway truck
air brake system?. Answer: FMVSS 121
⩥ If a truck is FMVSS 121 compliant, which of the following air
reservoirs must be incorporated into the air brake circuit?. Answer:
Supply, primary and secondary tanks
⩥ In a truck air brake system which sub circuit is primarily responsible
for actuating front axle service brakes when the system is functioning
normally?. Answer: Secondary circuit
⩥ When a FMVSS 121 compliant tractor trailer combination is moving
down the highway at a speed of 50 mph, which circuit must be charged
with air?. Answer: Hold off circuit
⩥ What best describes the functions of a tractor protection valve?.
Answer: Pressure protects the tractor air supply in the event of loss of
pressure in a trailer
, Routes trailer supply air and service application signal to the trailer
pneumatic circuits
Blocks service signal air to the trailer until trailer air supply is activated
⩥ If you have yo make an adjustment to air system cut off pressure
where should the adjustment be made?. Answer: The governor
⩥ How is the relay section of an FMVSS 121 compliant duel circuit foot
valve activated when the air brake is functioning properly?. Answer:
Pneumatically
⩥ What is the function of a quick release gladhand when used?. Answer:
Speeds service brake release timing
⩥ What best accounts for brake feel in an air brake system?. Answer:
Resistance of application pressure versus for pressure
⩥ What is the potential energy of an air brake system?. Answer:
Compressed air
⩥ When a tractor spring brake assembly is charged with air on both its
service and hold off chambers what results is known as?. Answer:
Compounding
