Michigan CDL Air Brakes Exam
QUESTIONS AND ANSWERS 100%
RATED CORRECT WITH 100% SURE
PASS|GRADED A+
3 different braking systems that make up Air Brakes - CORRECT ANSWERS Service Brake,
Parking Brake, Emergency Brake
Air Compressor - CORRECT ANSWERS Pumps air into storage tanks and connected to the
engine via gears or a v-belt.
Air Compressor Governor - CORRECT ANSWERS Controls when the air compressor will pump
air into the air storage tanks. When tank pressure rises to the cut-out level, the governor stops the
compressor from pumping. When the tank pressure falls to the cut-in level, the governor allow the
compressor to pump again.
Cut-Out Level - CORRECT ANSWERS 125 PSI (Governor stops the compressor from pumping
air)
Cut-In Level - CORRECT ANSWERS 100 PSI (Governor allows compressor to start pumping
again)
Air Storage Tanks - CORRECT ANSWERS Holds the compressed air.
Air Tank Drains - CORRECT ANSWERS Valve to drain oil and water from the tanks.
Alcohol Evaporator - CORRECT ANSWERS Puts alcohol into the air system to reduce risk of
ice in the valves.
, Safety Valve - CORRECT ANSWERS In the first take air is pumped in to...protects the tank and
system from too much pressure. Set to open at 150 PSI.
Foundation Brakes - CORRECT ANSWERS Used at each wheel...most common type is the S-
Cam drum brake.
Drums, Shoes and Linings - CORRECT ANSWERS Drums located on each end of the axles.
Wheels are bolted to the drums. To stop, the brake shoes and linings are pushed against the inside of
the drum.
S-Cam Brakes - CORRECT ANSWERS Pressure pushes the rod out, moving the slack adjuster,
thus twisting the brake camshaft. Forces the brake shoes away from one another and presses them
against the inside of the brake drum.
Supply Pressure Gauges - CORRECT ANSWERS Tells you how much pressure is in the air
tanks. Will be one for each half the the brake system in dual air brake systems.
Application Pressure Gauge - CORRECT ANSWERS Shows how much pressure you are
applying to brakes. (Not on all vehicles). Increasing pressure to hold same speed means brakes are
fading. Slow down and use lower gear.
Causes for increased pressure: - CORRECT ANSWERS Brakes out of adjustment, Air leaks,
Mechanical problems
Low Air Pressure Warning - CORRECT ANSWERS Required on all vehicles with air brakes.
Signal that must come on before the pressure in tanks falls below 60 PSI.
Spring Brakes - CORRECT ANSWERS Used for emergency brakes and parking brakes. Held
back by air pressure. If pressure removed, the springs put on the brakes. In tractors and straight trucks,
these will come on when air pressure drops to 20 - 45 PSI (typically 20 - 30 PSI).
QUESTIONS AND ANSWERS 100%
RATED CORRECT WITH 100% SURE
PASS|GRADED A+
3 different braking systems that make up Air Brakes - CORRECT ANSWERS Service Brake,
Parking Brake, Emergency Brake
Air Compressor - CORRECT ANSWERS Pumps air into storage tanks and connected to the
engine via gears or a v-belt.
Air Compressor Governor - CORRECT ANSWERS Controls when the air compressor will pump
air into the air storage tanks. When tank pressure rises to the cut-out level, the governor stops the
compressor from pumping. When the tank pressure falls to the cut-in level, the governor allow the
compressor to pump again.
Cut-Out Level - CORRECT ANSWERS 125 PSI (Governor stops the compressor from pumping
air)
Cut-In Level - CORRECT ANSWERS 100 PSI (Governor allows compressor to start pumping
again)
Air Storage Tanks - CORRECT ANSWERS Holds the compressed air.
Air Tank Drains - CORRECT ANSWERS Valve to drain oil and water from the tanks.
Alcohol Evaporator - CORRECT ANSWERS Puts alcohol into the air system to reduce risk of
ice in the valves.
, Safety Valve - CORRECT ANSWERS In the first take air is pumped in to...protects the tank and
system from too much pressure. Set to open at 150 PSI.
Foundation Brakes - CORRECT ANSWERS Used at each wheel...most common type is the S-
Cam drum brake.
Drums, Shoes and Linings - CORRECT ANSWERS Drums located on each end of the axles.
Wheels are bolted to the drums. To stop, the brake shoes and linings are pushed against the inside of
the drum.
S-Cam Brakes - CORRECT ANSWERS Pressure pushes the rod out, moving the slack adjuster,
thus twisting the brake camshaft. Forces the brake shoes away from one another and presses them
against the inside of the brake drum.
Supply Pressure Gauges - CORRECT ANSWERS Tells you how much pressure is in the air
tanks. Will be one for each half the the brake system in dual air brake systems.
Application Pressure Gauge - CORRECT ANSWERS Shows how much pressure you are
applying to brakes. (Not on all vehicles). Increasing pressure to hold same speed means brakes are
fading. Slow down and use lower gear.
Causes for increased pressure: - CORRECT ANSWERS Brakes out of adjustment, Air leaks,
Mechanical problems
Low Air Pressure Warning - CORRECT ANSWERS Required on all vehicles with air brakes.
Signal that must come on before the pressure in tanks falls below 60 PSI.
Spring Brakes - CORRECT ANSWERS Used for emergency brakes and parking brakes. Held
back by air pressure. If pressure removed, the springs put on the brakes. In tractors and straight trucks,
these will come on when air pressure drops to 20 - 45 PSI (typically 20 - 30 PSI).
