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SAAQ mention F air brake test: 12 sample questions with answers

Twelve practice questions on the air brake system, with the answer and explanation under each one.

Good to know: mention F has its own knowledge test, with a 75% pass mark (SAAQ brochure). These 12 questions are original examples written from chapters 4 and 5 of the official guide; they are not in the app’s question bank. About the mention: mention F: what to expect.

These questions are original (not official SAAQ questions); the answer is shown under each question.

Question 1

On a drum brake the gap between the linings and the drum is too large, but the gauges show normal air pressure. What can you conclude?

  1. A The brake is effective, because the air pressure is correct
  2. B The brake will be ineffective even with correct air pressure
  3. C The brake is effective only as a parking brake
  4. D The brake is effective only as an emergency brake
Answer

Answer: B — The brake will be ineffective even with correct air pressure

Poorly adjusted brakes are always ineffective, whether used as the service, parking or emergency brake: if the gap is too large, the pressure on the drum is insufficient even when the air pressure is correct.

Source: Conduire un véhicule lourd (SAAQ guide, 10th ed., French), ch. 4, “L’ajustement des freins”

Question 2

In the preventive slack-take-up procedure described in the guide, which conditions must be met before you press the brake pedal fully?

  1. A The brakes must be hot
  2. B The parking brakes must be applied
  3. C The air pressure must be at the minimum
  4. D The brakes must be cold, the parking brakes released and the air pressure at the maximum
Answer

Answer: D — The brakes must be cold, the parking brakes released and the air pressure at the maximum

The procedure calls for cold brakes, released parking brakes and air pressure at the maximum (120 psi or 827 kPa), then a full press of the pedal for five seconds, repeated four or five times. It is not mandatory.

Source: Conduire un véhicule lourd (SAAQ guide, 10th ed., French), ch. 4, “Procédure préventive de rattrapage”

Question 3

In general, the air compressor starts when the pressure in the service reservoirs drops below about:

  1. A 724 kPa (105 psi)
  2. B 345 kPa (50 psi)
  3. C 1,034 kPa (150 psi)
  4. D 1,379 kPa (200 psi)
Answer

Answer: A — 724 kPa (105 psi)

The guide gives the most common range: cut-in below 724 kPa (105 psi) and cut-out at 862 kPa (125 psi), a swing of 138 kPa (20 psi). Some systems work at other levels.

Source: Conduire un véhicule lourd (SAAQ guide, 10th ed., French), ch. 5, “Le compresseur d’air et le régulateur de pression”

Question 4

In winter, when is it best to drain the air reservoirs?

  1. A Before starting in the morning, when the vehicle is cold
  2. B Only once a week
  3. C After using the vehicle, while it is still warm
  4. D Never, because water freezes in the valves
Answer

Answer: C — After using the vehicle, while it is still warm

In winter it is best to drain after use, while the vehicle is still warm, to reduce the risk of a frozen drain valve staying open. Draining is done daily.

Source: Conduire un véhicule lourd (SAAQ guide, 10th ed., French), ch. 5, “La vidange des réservoirs”

Question 5

What is the common drum brake type on heavy vehicles called, in which a cam spreads the brake shoes?

  1. A C-cam brake
  2. B S-cam brake
  3. C Z-cam brake
  4. D O-cam brake
Answer

Answer: B — S-cam brake

The widespread drum brake is an S-cam brake: a cam shaped like an S spreads the brake shoes against the drum.

Source: Conduire un véhicule lourd (SAAQ guide, 10th ed., French), ch. 5, “Le frein à tambour”

Question 6

In which type of heavy vehicle is the disc brake most used, according to the guide?

  1. A Dump trucks
  2. B Road tractors
  3. C Motorcoaches
  4. D Trailers
Answer

Answer: C — Motorcoaches

The guide says the disc brake is the most used type in motorcoaches, and is found more and more in other heavy vehicles.

Source: Conduire un véhicule lourd (SAAQ guide, 10th ed., French), ch. 5, “Le frein à disque”

Question 7

When you couple a tractor to a semi-trailer, how do you connect the coupling heads?

  1. A Those of the same colour together
  2. B In any order, since they are all interchangeable
  3. C Those of different colours together, to balance the air
  4. D Only one head; the other can safely stay free
Answer

Answer: A — Those of the same colour together

You connect the matching heads (same colour) together: place them against each other at a 90° angle, then rotate them to align the hoses.

Source: Conduire un véhicule lourd (SAAQ guide, 10th ed., French), ch. 5, “Les canalisations de liaison”

Question 8

Where does the air that fills a semi-trailer’s reservoirs come from?

  1. A From a compressor on the semi-trailer
  2. B Directly from the supply reservoir, without going anywhere else
  3. C From the brake pedal
  4. D From the service reservoirs of the truck or tractor
Answer

Answer: D — From the service reservoirs of the truck or tractor

The trailer and semi-trailer have their own reservoirs, supplied by the service reservoirs of the truck or tractor (the towing vehicle’s compressor fills them this way).

Source: Conduire un véhicule lourd (SAAQ guide, 10th ed., French), ch. 5, “Les réservoirs d’air comprimé”

Question 9

After the coupling manoeuvre, what can the semi-trailer’s hand brake control be used for?

  1. A To replace the parking brake overnight
  2. B To check that the semi-trailer’s service brake works
  3. C To slow down on hills
  4. D To fill the semi-trailer’s reservoirs
Answer

Answer: B — To check that the semi-trailer’s service brake works

This control applies the service brake on the semi-trailer wheels only. It is sometimes used to check that the coupling was done properly and to test the semi-trailer’s service brake after coupling.

Source: Conduire un véhicule lourd (SAAQ guide, 10th ed., French), ch. 5, “La commande de freinage à main de la semi-remorque”

Question 10

On a truck or tractor, where is the parking brake mounted?

  1. A Only on the rear wheels
  2. B On all wheels, front and rear
  3. C Only on the front wheels
  4. D On a single rear wheel
Answer

Answer: A — Only on the rear wheels

The parking brake is mounted only on the rear wheels of the tractor, truck or bus, and it is always paired with a service brake (a double brake chamber).

Source: Conduire un véhicule lourd (SAAQ guide, 10th ed., French), ch. 5, “Les récepteurs de freinage”

Question 11

The air compressor fails while you are driving. What happens, according to the guide?

  1. A The service brake stops working immediately
  2. B The service brake keeps working indefinitely thanks to the reservoirs
  3. C The service brake may work for a while, then the air reserve can run out and the emergency brake applies
  4. D Only the parking brake remains usable
Answer

Answer: C — The service brake may work for a while, then the air reserve can run out and the emergency brake applies

The reservoirs let the service brake work for a while, but the reserve can run out quickly. The low-pressure indicator warns you, then the emergency brake starts to apply: park the vehicle as soon as you get the signal.

Source: Conduire un véhicule lourd (SAAQ guide, 10th ed., French), ch. 5, “Les réservoirs d’air comprimé”

Question 12

In an air brake system, where does the braking force come from?

  1. A From the driver’s muscle force on the pedal
  2. B From the pressure of the compressed air
  3. C From the engine, through a belt
  4. D From the weight of the load
Answer

Answer: B — From the pressure of the compressed air

Here it is not the driver’s muscle that brakes, as in a hydraulic system: compressed air pushes in the brake chambers. The further you press the pedal, the more air enters.

Source: Conduire un véhicule lourd (SAAQ guide, 10th ed., French), ch. 5, “Les récepteurs de freinage”

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Practice questions from an independent product, current as of 2026-11-01. If in doubt, the official text prevails: check saaq.gouv.qc.ca.