A front tire fails the inspection if the tread depth on two adjacent grooves anywhere on the tire is less than
- 1.5 millimeters (0.06 inches)
- 15 millimeters (0.59 inches)
- 6 millimeters (0.24 inches)
- 3 millimeters (0.12 inches) ✓
Answer: D. 3 millimeters (0.12 inches)
A front tire fails inspection when the tread depth in two adjacent grooves is less than 3 millimetres (0.12 inches).
Why this is the answer
The handbook says front tires on a vehicle with a gross vehicle rating over 4,500 kilograms must have at least 3 millimetres of tread measured in two adjacent tread grooves. If the tread is below that minimum, the tire does not meet the stated front-tire requirement. The same passage gives a lower 1.5 millimetre minimum for rear tires, so the front-tire rule is the one that applies here.
Why the other answers are wrong
- A. 1.5 millimeters (0.06 inches) — 1.5 millimetres is the rear-tire minimum in the passage, not the front-tire minimum.
- B. 15 millimeters (0.59 inches) — 15 millimetres is far above any tread minimum mentioned in the passage and is not the front-tire rule.
- C. 6 millimeters (0.24 inches) — 6 millimetres is not the front-tire minimum stated in the passage; the stated minimum is 3 millimetres.
Remember it
Front tires need the 3 millimetre figure in two adjacent grooves; keep the smaller 1.5 millimetre figure for rear tires.