KS · L (restriction removed) Endorsement

Kansas Air Brakes CDL Practice Test

Below are 25 exam-style questions for the Kansas Air Brakes CDL knowledge test, modeled on the FMCSA-aligned content used by the Kansas Department of Revenue Division of Vehicles. Try to answer each question on your own before reading the answer key directly under it. The questions and answer choices are shuffled deterministically per state and endorsement, so the order will stay the same on repeat visits — that lets you genuinely measure your improvement.

Heads up: this is a study tool, not a graded exam. Cover the answer with your hand or a sheet of paper for an honest practice run, then re-read the explanations for any questions you missed. Aim for 22 out of 25 or better, three times in a row, before scheduling the real exam.

Question 1 of 25

During the seven-step air-brake check, the final step is to:

A Pull forward and apply the foot brake to test for stopping
B Adjust the slack adjusters
C Drain the wet tank
D Check tire pressures

Correct answer: A

After all stationary tests, perform a moving brake check at low speed to verify the service brakes stop the vehicle.

Question 2 of 25

You should NOT drain the wet tank when:

A The vehicle is in motion
B It is full of moisture
C You are about to begin a trip
D There is no situation in which draining is wrong

Correct answer: D

Daily draining is a routine task; there is no situation where draining is unsafe (other than while driving).

Question 3 of 25

A common reason for compressor failure to keep up is:

A A leak in the brake system
B A clogged air filter or worn compressor
C A broken governor
D All of the above

Correct answer: D

Any of these causes can prevent the compressor from maintaining cut-out pressure.

Question 4 of 25

Slack adjusters should be checked because:

A They control trailer height
B They are decorative
C They affect engine performance
D Out-of-adjustment slack adjusters can result in brakes that do not work properly

Correct answer: D

Slack adjusters convert pushrod motion into braking force. Out-of-adjustment slack adjusters reduce braking ability and are a common out-of-service item.

Question 5 of 25

When applying the foot brake hard:

A The compressor cuts out
B Air pressure should remain unchanged
C Air pressure increases
D Air pressure may drop slightly

Correct answer: D

A small drop is expected during heavy application. The compressor recharges the system back up to cut-out pressure.

Question 6 of 25

Spring brakes do NOT replace:

A The headlights
B The horn
C The tail lights
D The service brakes for normal stops

Correct answer: D

Spring brakes are for parking and emergency only — never for normal service braking.

Question 7 of 25

When doing the air-leak rate test, the engine should be:

A Off, with brakes released for the first part
B Running at high RPM
C In gear
D Started and stopped repeatedly

Correct answer: A

Engine off, brakes released to test static leak rate; then brakes applied and held for the second part.

Question 8 of 25

Front-wheel brakes are required on commercial vehicles because:

A They make steering easier
B They reduce stopping distance significantly without normally causing skids on dry pavement
C They look balanced
D Federal law mandates them as decorative

Correct answer: B

Front brakes provide a large share of stopping force and modern vehicles are designed so they do not cause front-wheel skids on dry pavement.

Question 9 of 25

When approaching a long downgrade, you should:

A Test the brakes by lightly applying them at the top
B Test the brakes at the bottom
C Skip the brake test
D Coast in neutral

Correct answer: A

A light brake application at the top tests for pulling or weakness before the descent puts heat into the system.

Question 10 of 25

Stopping a vehicle with an air-brake failure can sometimes be done by:

A Using the trailer hand valve, then engine braking, then a runaway ramp if needed
B Coasting in neutral
C Putting the transmission in reverse
D Honking

Correct answer: A

In an air-brake failure, the trailer hand valve can still apply the trailer service brakes, then engine braking and a runaway ramp.

Question 11 of 25

After making the initial brake application, the air-pressure drop should not exceed:

A 2-3 psi
B 5 psi
C 1 psi
D 10 psi

Correct answer: A

A small initial drop is normal as the system equalizes — but excessive drop indicates a leak.

Question 12 of 25

The proper braking technique on a long downgrade is:

A Heavy continuous braking
B Apply the parking brake
C Coast in neutral
D Light, intermittent braking with engine braking and a low gear

Correct answer: D

Use the proper low gear so engine braking does most of the work; brief, moderate brake applications keep the speed in check.

Question 13 of 25

Spring brakes are held off by:

A Air pressure
B Engine vacuum
C Hydraulic pressure
D Electrical current

Correct answer: A

Compressed air holds the springs back. When air pressure drops, the springs apply the brakes mechanically.

Question 14 of 25

A correctly adjusted brake will have:

A No slack adjuster
B Pushrod travel within the legal limit for that brake type
C Loose drum bolts
D Visible rust

Correct answer: B

Pushrod travel must be within the manufacturer's and federal limits — exact value depends on chamber size.

Question 15 of 25

Air pressure should normally build from 50 to 90 psi within:

A 10 minutes
B About 3 minutes in dual systems
C Less than 30 seconds
D It does not matter

Correct answer: B

Dual air systems should build from 50 to 90 psi within about 3 minutes at idle.

Question 16 of 25

Air-brake hoses should:

A Be wrapped in tape
B Have at least 5 splices each
C Show no signs of damage, leaks, or excessive wear
D Be coiled tightly under the truck

Correct answer: C

Damaged or chafed hoses are a common air-brake defect and a frequent out-of-service citation.

Question 17 of 25

A leaking air system on a parked truck is dangerous because:

A It can wake the driver
B When pressure drops far enough, spring brakes apply suddenly and the vehicle becomes unmovable
C The fuel will leak
D The engine will not start

Correct answer: B

A bigger problem is en route: if a slow leak goes unnoticed and pressure drops below the spring-brake set point, the brakes apply on the road.

Question 18 of 25

A common practice during a long brake-recharge wait is to:

A Disable the warning lamp
B Allow the system to reach operating pressure before driving
C Check the brake light visibility
D Drain the wet tank

Correct answer: B

Always wait for full operating pressure (typically around 120 psi) before moving the vehicle.

Question 19 of 25

When applying brakes in an emergency without ABS:

A Pump rapidly and lightly
B Use stab braking — apply hard, release when wheels lock, re-apply
C Use only the parking brake
D Press as hard as possible and hold

Correct answer: B

Stab braking keeps the truck straight in an emergency without ABS. Hard continuous pressure can lock the wheels and cause a jackknife.

Question 20 of 25

When the air pressure in the brake system drops too low:

A The trailer hand valve releases
B Nothing happens until you stop
C Spring brakes apply automatically
D The engine stops

Correct answer: C

When system pressure drops, typically below 20-45 psi, mechanical springs apply the brakes regardless of driver input.

Question 21 of 25

You should test the trailer service brakes by:

A Looking at the gauge
B Releasing the parking brakes, moving the vehicle slowly forward, and applying the trailer hand valve
C Listening for a hiss
D Pumping them while parked

Correct answer: B

A low-speed pull-and-stop with the trailer hand valve confirms the trailer brakes apply on their own.

Question 22 of 25

Brake fade is most likely caused by:

A Heat from continuous brake use on long downgrades
B Too much air pressure
C Worn-out hoses
D Cold weather

Correct answer: A

Heat reduces friction and brake effectiveness. Use a low gear so the engine, not the service brakes, holds the load.

Question 23 of 25

You should test the service brakes by:

A Driving at 30 mph and slamming on the brakes
B At about 5 mph, applying the brake firmly and feeling for pulling, sticking, or unusual feel
C Listening to the air gauge
D Pumping the brakes

Correct answer: B

A low-speed brake test catches sticking, pulling, or weak brakes before you build up speed.

Question 24 of 25

The total stopping distance for an air-brake equipped vehicle is:

A Perception + braking distance
B Reaction distance + braking distance
C Reaction + braking + brake-lag distance
D Perception + reaction + brake-lag + braking distance

Correct answer: D

Air brakes add a brake-lag distance — the time from foot-pressure to actual brake application — that hydraulic systems do not have.

Question 25 of 25

A dual air-brake system means:

A Twice the air pressure
B Two governors
C Two compressors
D Two separate air-brake systems on one set of brake controls

Correct answer: D

Modern trucks have two separate air systems (often labeled primary and secondary) with one set of brake controls so a failure in one circuit still leaves working brakes.

Study tips for the Kansas Air Brakes exam

The Air Brakes portion of the Kansas CDL exam is graded out of the bank of questions the Kansas Department of Revenue Division of Vehicles draws from each year. While the exact bank is not published, every question is sourced from the Air Brakes chapter of the Kansas CDL handbook, which itself is derived from the FMCSA Model Commercial Driver's License Manual. That means studying our practice tests, reading the corresponding handbook chapter, and re-reading the parts you got wrong is genuinely the most efficient route to a first-time pass.

Most successful applicants follow a simple cycle: take the practice test cold, write down every question you missed, open the matching chapter of the official Kansas handbook, re-read the section that contains the right answer, then re-take the practice test 24 to 48 hours later. The 24-hour delay matters — sleep is when your brain commits new information to long-term memory, and CDL knowledge questions reward that kind of consolidated learning rather than cramming.

Pay particular attention to questions that include qualifier words like always, never, only, primary, or most. CDL test writers love to flip the right answer with a single qualifier. When two answer choices look almost identical, pay attention to the verb (is it must, should, or may?) and to any numbers (14 days, 100 air miles, 8 hours, 70/8 split). On endorsement tests in particular, watch for trick framing where a true statement about a different endorsement is offered as the "correct" answer to a question that is actually about Air Brakes.

Test-day logistics matter too. Bring photo ID, your Social Security card or birth certificate, your medical examiner's certificate (DOT card), and proof of state residency if you haven't already submitted those documents. The Kansas Department of Revenue Division of Vehicles will not let you sit for the knowledge exam without your documentation, and most offices charge an additional fee for re-attempts. Arrive early — the wait at most CDL testing offices runs 30 to 60 minutes — and silence your phone before the exam begins.

Finally, keep your General Knowledge fundamentals sharp even when you're focused on the Air Brakes exam. Many states administer multiple knowledge tests in a single sitting, and questions on weight definitions (GVWR, GCWR, GAWR), stopping distance, and the pre-trip inspection routine show up across endorsements. If you're unsure on the basics, sit a fresh Kansas General Knowledge practice test before scheduling the real exam.

Next steps

Missed more than four questions? Re-read the Air Brakes study guide and the matching chapter in the official Kansas CDL handbook. Then come back and re-take the test. Once you can score 22 of 25 or higher on three runs in a row, you're in good shape to schedule the real exam at your local Kansas Department of Revenue Division of Vehicles office.

Already comfortable with this endorsement? Drill another: KS General Knowledge · KS Combination Vehicles · KS Hazardous Materials · KS Passenger · KS School Bus · KS Tank Vehicle · KS Doubles / Triples

New to the CDL process in Kansas? Read How to apply for a CDL in Kansas for the document checklist and step-by-step timeline.