MICHIGAN CDL AIR BRAKES QUESTIONS
WITH CORRECT ANSWERS 2025
3UdifferentUbrakingUsystemsUthatUmakeUupUAirUBrakesU-UCORRECTUANSWERU-
ServiceUBrake,UParkingUBrake,UEmergencyUBrake
AirUCompressorU-UCORRECTUANSWERU-
PumpsUairUintoUstorageUtanksUandUconnectedUtoUtheUengineUviaUgearsUorUaUv-belt.
AirUCompressorUGovernorU-UCORRECTUANSWERU-
ControlsUwhenUtheUairUcompressorUwillUpumpUairUintoUtheUairUstorageUtanks.UWhenUtankUpressureUrisesUto
UtheUcut-
outUlevel,UtheUgovernorUstopsUtheUcompressorUfromUpumping.UWhenUtheUtankUpressureUfallsUtoUtheUcut-
inUlevel,UtheUgovernorUallowUtheUcompressorUtoUpumpUagain.
Cut-OutULevelU-UCORRECTUANSWERU-125UPSIU(GovernorUstopsUtheUcompressorUfromUpumpingUair)
Cut-InULevelU-UCORRECTUANSWERU-100UPSIU(GovernorUallowsUcompressorUtoUstartUpumpingUagain)
AirUStorageUTanksU-UCORRECTUANSWERU-HoldsUtheUcompressedUair.
AirUTankUDrainsU-UCORRECTUANSWERU-ValveUtoUdrainUoilUandUwaterUfromUtheUtanks.
AlcoholUEvaporatorU-UCORRECTUANSWERU-
PutsUalcoholUintoUtheUairUsystemUtoUreduceUriskUofUiceUinUtheUvalves.
SafetyUValveU-UCORRECTUANSWERU-
InUtheUfirstUtakeUairUisUpumpedUinUto...protectsUtheUtankUandUsystemUfromUtooUmuchUpressure.USetUtoUope
nUatU150UPSI.
FoundationUBrakesU-UCORRECTUANSWERU-UsedUatUeachUwheel...mostUcommonUtypeUisUtheUS-
CamUdrumUbrake.
, Drums,UShoesUandULiningsU-UCORRECTUANSWERU-
DrumsUlocatedUonUeachUendUofUtheUaxles.UWheelsUareUboltedUtoUtheUdrums.UToUstop,UtheUbrakeUshoesUan
dUliningsUareUpushedUagainstUtheUinsideUofUtheUdrum.
S-CamUBrakesU-UCORRECTUANSWERU-
PressureUpushesUtheUrodUout,UmovingUtheUslackUadjuster,UthusUtwistingUtheUbrakeUcamshaft.UForcesUtheUb
rakeUshoesUawayUfromUoneUanotherUandUpressesUthemUagainstUtheUinsideUofUtheUbrakeUdrum.
SupplyUPressureUGaugesU-UCORRECTUANSWERU-
TellsUyouUhowUmuchUpressureUisUinUtheUairUtanks.UWillUbeUoneUforUeachUhalfUtheUtheUbrakeUsystemUinUdualU
airUbrakeUsystems.
ApplicationUPressureUGaugeU-UCORRECTUANSWERU-
ShowsUhowUmuchUpressureUyouUareUapplyingUtoUbrakes.U(NotUonUallUvehicles).UIncreasingUpressureUtoUhol
dUsameUspeedUmeansUbrakesUareUfading.USlowUdownUandUuseUlowerUgear.
CausesUforUincreasedUpressure:U-UCORRECTUANSWERU-
BrakesUoutUofUadjustment,UAirUleaks,UMechanicalUproblems
LowUAirUPressureUWarningU-UCORRECTUANSWERU-
RequiredUonUallUvehiclesUwithUairUbrakes.USignalUthatUmustUcomeUonUbeforeUtheUpressureUinUtanksUfallsUbe
lowU60UPSI.
SpringUBrakesU-UCORRECTUANSWERU-
UsedUforUemergencyUbrakesUandUparkingUbrakes.UHeldUbackUbyUairUpressure.UIfUpressureUremoved,UtheUsp
ringsUputUonUtheUbrakes.UInUtractorsUandUstraightUtrucks,UtheseUwillUcomeUonUwhenUairUpressureUdropsUtoU
20U-U45UPSIU(typicallyU20U-U30UPSI).
DualUAirUBrakesU-UCORRECTUANSWERU-
HasUtwoUseparateUairUbrakeUsystemsU(PrimaryUandUSecondary),UwhichUuseUaUsingleUsetUofUbrakeUcontrols.U
EachUhasUitsUownUtanks,Uhoses,Ulines,Uetc.
MinimumUpressureUbeforeUdrivingUinUPrimaryUandUSecondaryUsystemsU-UCORRECTUANSWERU-100UPSI
WITH CORRECT ANSWERS 2025
3UdifferentUbrakingUsystemsUthatUmakeUupUAirUBrakesU-UCORRECTUANSWERU-
ServiceUBrake,UParkingUBrake,UEmergencyUBrake
AirUCompressorU-UCORRECTUANSWERU-
PumpsUairUintoUstorageUtanksUandUconnectedUtoUtheUengineUviaUgearsUorUaUv-belt.
AirUCompressorUGovernorU-UCORRECTUANSWERU-
ControlsUwhenUtheUairUcompressorUwillUpumpUairUintoUtheUairUstorageUtanks.UWhenUtankUpressureUrisesUto
UtheUcut-
outUlevel,UtheUgovernorUstopsUtheUcompressorUfromUpumping.UWhenUtheUtankUpressureUfallsUtoUtheUcut-
inUlevel,UtheUgovernorUallowUtheUcompressorUtoUpumpUagain.
Cut-OutULevelU-UCORRECTUANSWERU-125UPSIU(GovernorUstopsUtheUcompressorUfromUpumpingUair)
Cut-InULevelU-UCORRECTUANSWERU-100UPSIU(GovernorUallowsUcompressorUtoUstartUpumpingUagain)
AirUStorageUTanksU-UCORRECTUANSWERU-HoldsUtheUcompressedUair.
AirUTankUDrainsU-UCORRECTUANSWERU-ValveUtoUdrainUoilUandUwaterUfromUtheUtanks.
AlcoholUEvaporatorU-UCORRECTUANSWERU-
PutsUalcoholUintoUtheUairUsystemUtoUreduceUriskUofUiceUinUtheUvalves.
SafetyUValveU-UCORRECTUANSWERU-
InUtheUfirstUtakeUairUisUpumpedUinUto...protectsUtheUtankUandUsystemUfromUtooUmuchUpressure.USetUtoUope
nUatU150UPSI.
FoundationUBrakesU-UCORRECTUANSWERU-UsedUatUeachUwheel...mostUcommonUtypeUisUtheUS-
CamUdrumUbrake.
, Drums,UShoesUandULiningsU-UCORRECTUANSWERU-
DrumsUlocatedUonUeachUendUofUtheUaxles.UWheelsUareUboltedUtoUtheUdrums.UToUstop,UtheUbrakeUshoesUan
dUliningsUareUpushedUagainstUtheUinsideUofUtheUdrum.
S-CamUBrakesU-UCORRECTUANSWERU-
PressureUpushesUtheUrodUout,UmovingUtheUslackUadjuster,UthusUtwistingUtheUbrakeUcamshaft.UForcesUtheUb
rakeUshoesUawayUfromUoneUanotherUandUpressesUthemUagainstUtheUinsideUofUtheUbrakeUdrum.
SupplyUPressureUGaugesU-UCORRECTUANSWERU-
TellsUyouUhowUmuchUpressureUisUinUtheUairUtanks.UWillUbeUoneUforUeachUhalfUtheUtheUbrakeUsystemUinUdualU
airUbrakeUsystems.
ApplicationUPressureUGaugeU-UCORRECTUANSWERU-
ShowsUhowUmuchUpressureUyouUareUapplyingUtoUbrakes.U(NotUonUallUvehicles).UIncreasingUpressureUtoUhol
dUsameUspeedUmeansUbrakesUareUfading.USlowUdownUandUuseUlowerUgear.
CausesUforUincreasedUpressure:U-UCORRECTUANSWERU-
BrakesUoutUofUadjustment,UAirUleaks,UMechanicalUproblems
LowUAirUPressureUWarningU-UCORRECTUANSWERU-
RequiredUonUallUvehiclesUwithUairUbrakes.USignalUthatUmustUcomeUonUbeforeUtheUpressureUinUtanksUfallsUbe
lowU60UPSI.
SpringUBrakesU-UCORRECTUANSWERU-
UsedUforUemergencyUbrakesUandUparkingUbrakes.UHeldUbackUbyUairUpressure.UIfUpressureUremoved,UtheUsp
ringsUputUonUtheUbrakes.UInUtractorsUandUstraightUtrucks,UtheseUwillUcomeUonUwhenUairUpressureUdropsUtoU
20U-U45UPSIU(typicallyU20U-U30UPSI).
DualUAirUBrakesU-UCORRECTUANSWERU-
HasUtwoUseparateUairUbrakeUsystemsU(PrimaryUandUSecondary),UwhichUuseUaUsingleUsetUofUbrakeUcontrols.U
EachUhasUitsUownUtanks,Uhoses,Ulines,Uetc.
MinimumUpressureUbeforeUdrivingUinUPrimaryUandUSecondaryUsystemsU-UCORRECTUANSWERU-100UPSI
