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Manitoba Commercial: Tires, wheels, passing and intersections

Tread depth limits, retreads, tire pressure and heat, wheel fasteners and failures, passing and being passed, lane changes, curves and intersection rules for large vehicles.

  • 12 questions
  • Topic drill
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Tires, wheels, passing and intersections · Question 1Score 0/0

What is the minimum tread depth on the rear tires of a heavy truck (4,500 kg GVWR or more)?

Study reference: MPI Professional Driver's Manual (PDF, Dec. 2025), Ch. 2 Efficient and safe vehicle operation — Checking tires, wheels and fasteners, Passing, Lane changing, Curves, Intersections

All 12 questions in this test

Every question and its answer choices. The correct answers and explanations appear when you take the test above.

  1. What is the minimum tread depth on the rear tires of a heavy truck (4,500 kg GVWR or more)?

    1. 4 mm
    2. 2 mm
    3. 1 mm
    4. 3 mm

  2. A large vehicle that relies only on mirrors needs to cross several lanes. How should it change lanes?

    1. Through an intersection where it is wider
    2. One lane at a time, with full checks each time
    3. Across solid lines if no one is near
    4. All lanes at once to save time

  3. Why can lug nuts loosen after a tire has been installed?

    1. The tire pressure slowly pushes the nuts off the studs
    2. Rims heat and cool, which loosens the nuts
    3. Lug nuts always loosen after one trip
    4. Road salt dissolves the nut threads

  4. What is the only sure way to know tire pressure is correct?

    1. Kicking each tire firmly
    2. Checking the dash warning light
    3. Looking at the tire bulge
    4. Using a tire gauge

  5. On a truck with a GVWR of 4,500 kg or more, what is the minimum tread depth on the front steering tires?

    1. 5 mm
    2. 2 mm
    3. 3 mm
    4. 1.6 mm

  6. During your pre-trip you find a loose lug nut with a wrench. What should happen?

    1. Tighten it by hand and continue driving to the delivery
    2. Have a qualified technician inspect it
    3. Note it and check again next week
    4. Drive slowly to your destination

  7. Where may retreaded tires not be used?

    1. On steering axles
    2. On any school vehicle
    3. On drive axles
    4. On trailer axles

  8. A smaller vehicle pulls out to pass you. What should you do?

    1. Flash your headlights to warn it
    2. Speed up to keep the gap ahead
    3. Reduce speed to help it pass safely
    4. Wave it back into line behind you

  9. Two vehicles reach an uncontrolled intersection together. Who yields?

    1. The larger vehicle always has priority over smaller ones
    2. The vehicle on the left yields to the right
    3. Whoever is going straight has priority
    4. The vehicle on the right yields to the left

  10. When a whole wheel assembly separates, what is the usual cause?

    1. A worn brake lining
    2. A tire with low pressure
    3. A wheel bearing failure
    4. A missing mud flap

  11. Why avoid passing when your speed is only slightly higher than the other vehicle's?

    1. It wears out the transmission faster
    2. It is illegal on all Manitoba highways
    3. You stay in the fast lane too long and traffic bunches
    4. The other vehicle must legally speed up while you pass it

  12. Why is braking in a curve dangerous for a large vehicle?

    1. It adds to centrifugal force; rollover risk
    2. It turns off the ABS warning light
    3. It cools the brakes too quickly and cracks the drums
    4. It moves the load toward the cab

Tires, wheels, passing and intersections: key rules to remember

Our summary of what the official handbook says on this topic, in our own words. Read it before or after the practice questions above, then check the original chapter. Read the official chapter ↗

Ch. 2 Tires, wheels and fasteners (pp. 34–35)

  • Bald or damaged tires may not be used; check tires before each trip with a gauge.
  • Buses, trucks and tractors 4,500 kg GVWR or more: at least 3 mm tread on front steering tires and 2 mm on rear tires; under 4,500 kg: 1.6 mm on all tires.
  • Retreaded tires may not be used on steering axles; do not mix radial and non-radial tires or sizes on an axle.
  • Over-inflation wears the centre; under-inflation wears the edges and raises the hydroplaning risk.
  • Never bleed air from a warm tire; check and adjust pressure cold.
  • Lug nuts loosen as rims heat and cool; retorque after a rim is reinstalled (about 210–260 ft-lb on cast spoke wheels, 450–500 ft-lb on disc wheels).
  • A loose lug nut found during a pre-trip means a qualified technician must inspect the unit.
  • Whole-wheel separations usually come from bearing failure; warning signs are oil leaks and very hot hubs.
  • A separated wheel travels faster than the vehicle; a truck tire weighs about 181 kg.

Ch. 2 Passing, lane changes, curves (pp. 36–37)

  • Do not stay in the passing lane longer than needed; a small speed difference causes bunching.
  • Turbulence is felt beside the saddle tanks and near the rear of the trailer.
  • Do not wave other drivers past; when they pass, slow down to help them.
  • Lane change: mirrors, signal, mirrors again including convex, check the blind spot, keep signalling until fully in the lane.
  • Vehicles that rely only on mirrors should change one lane at a time; never change lanes in intersections or over solid lines.
  • Braking in a curve adds to centrifugal force and can cause a rollover, skid or jackknife; slow down before the curve and apply slight power in it.

Ch. 2 Intersections (p. 38)

  • More collisions happen at intersections than anywhere else.
  • Never enter a limited-view intersection faster than you can stop; do not assume right of way.
  • A flashing or steady "don't walk" signal warns that a stale green will change.
  • At an uncontrolled intersection both drivers slow down and the vehicle on the left yields to the vehicle on the right.
  • Do not use your size to take the right of way.

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