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Ohio CDL practice test

Getting a commercial driver's licence in Ohio starts with the CDL knowledge tests. The content is federal: every state, Ohio included, writes its tests from the FMCSA CDL manual, so the general knowledge test has 50 questions, the endorsement tests have 20 to 30, and the passing score is 80% on each. The Ohio driver licensing agency administers the test; the rules behind it are published by the FMCSA. Try the free Ohio CDL practice questions below, then pick a full test.

Free Ohio CDL practice questions

Five questions from the general knowledge, air brakes and combination vehicles banks, the three tests most Ohio Class A applicants take first. Show the answer to read the explanation.

  1. The most common type of foundation brake on heavy vehicles is the:

    • S-cam drum brake
    • Wedge brake
    • Disc brake
    • Band brake
    Show answer
    Answer: A. S-cam drum brake

    In an S-cam brake, air pushes the push rod, which turns the slack adjuster and the S-shaped cam. The cam forces the brake shoes against the drum. Wedge and disc brakes are used less often.

    Source: FMCSA CDL Manual, Section 5.1.8 (Foundation Brakes)

  2. In an S-cam brake, what forces the brake shoes against the drum?

    • Hydraulic fluid in the wheel cylinder
    • Air pressure acting directly on the shoes
    • The S-shaped cam, turned by the slack adjuster, pushes the shoes apart
    • A wedge driven between the shoes by the push rod
    Show answer
    Answer: C. The S-shaped cam, turned by the slack adjuster, pushes the shoes apart

    Air enters the brake chamber and moves the push rod, which turns the slack adjuster and the S-cam. The cam spreads the shoes, and when the pedal is released, springs pull the shoes back.

    Source: FMCSA CDL Manual, Section 5.1.8 (S-cam Brakes)

  3. The brake chamber at each wheel:

    • Stores extra air for emergencies
    • Cools the brake drum
    • Measures air leakage
    • Turns air pressure into mechanical force that moves the push rod
    Show answer
    Answer: D. Turns air pressure into mechanical force that moves the push rod

    Air pushes on a diaphragm inside the chamber, which drives the push rod outward. That motion works the slack adjuster and cam, applying the brakes.

    Source: FMCSA CDL Manual, Section 5.1.8 (Foundation Brakes)

  4. The supply pressure gauge tells you:

    • How much air pressure is in the air tanks
    • How much pressure you are applying to the brakes
    • The pressure in the tires
    • The engine oil pressure
    Show answer
    Answer: A. How much air pressure is in the air tanks

    All air-brake vehicles have a supply pressure gauge. A dual system has either one gauge with two needles or two gauges, one for each system.

    Source: FMCSA CDL Manual, Section 5.1.9 (Supply Pressure Gauges)

  5. On a long downgrade you notice you must apply more and more pressure on the application pressure gauge to hold the same speed. This means:

    • The air compressor is working harder than usual
    • The brakes are adjusted too tightly
    • The brakes are fading, and you should slow down and use a lower gear
    • The road is getting steeper
    Show answer
    Answer: C. The brakes are fading, and you should slow down and use a lower gear

    Rising application pressure for the same braking effect is the sign of brake fade. The brakes are overheating, so reduce speed with a lower gear and let them cool.

    Source: FMCSA CDL Manual, Section 5.1.9 (Application Pressure Gauge)

Every CDL test for Ohio drivers

Each page has ten free sample questions, the real question count, the 80% pass mark and what the test covers.

How the Ohio CDL knowledge test works

You take the general knowledge test first; it is required for every CDL class. Class A drivers add the combination vehicles test. Almost everyone takes the air brakes test, because skipping it puts an air brake restriction on the licence. Endorsements (hazmat, tanker, doubles/triples, passenger, school bus) each have their own knowledge test. Pass the tests and you hold a commercial learner's permit; the skills test in a truck comes later.

Fees, appointment rules and test centre locations are set by Ohio and change over time, so check the state driver licensing agency before you go. What does not change is the content, and that is what PassRig drills.

Ohio CDL test questions

How many questions are on the Ohio CDL test?

The Ohio CDL general knowledge test follows the federal model: 50 questions, 40 correct to pass. Endorsement tests are shorter: air brakes 25, hazmat 30, and combination vehicles, tanker, doubles/triples, passenger and school bus 20 each.

What is the passing score on the Ohio CDL permit test?

80% on every knowledge test, the same pass mark used across the United States.

Where do I take the CDL knowledge test in Ohio?

At the Ohio state driver licensing agency (the DMV, DOT or equivalent). Check its website for locations, appointments and current fees; the test content itself comes from the FMCSA CDL manual.

Does PassRig have Ohio CDL practice questions?

Yes. Pick Ohio in the app and you get practice sets and mock exams built from the knowledge test content your state uses, with the real counts and the 80% line.

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