Question

Difficulty: HardTires, Wheels, and Rims Inspection

An operator conducting a mandatory pre-trip walk-around inspection on a commercial vehicle records the following specific tire conditions:

Wheel PositionMeasured Condition
Steer Axle (Front Left)5/325/32-inch tread depth in major grooves, valve stem cap secured
Steer Axle (Front Right)3/323/32-inch tread depth in major grooves, even wear across tread
Drive Axle (Forward Outer)3/323/32-inch tread depth in major grooves, no fabric exposed
Trailer Axle (Rear Duals)2/322/32-inch tread depth in major grooves, tires spaced evenly with no contact

Which of these recorded conditions fails federal commercial vehicle safety inspection standards and prohibits the vehicle from being driven?

  1. A
    The forward outer drive axle tire measured at 3/323/32-inch tread depth
  2. The front right steer axle tire measured at 3/323/32-inch tread depthAnswer
  3. C
    The rear dual trailer tires measured at 2/322/32-inch tread depth
  4. D
    The front left steer axle tire measured at 5/325/32-inch tread depth

Answer

The front right steer axle tire measured at 3/323/32-inch tread depth violates safety standards.
Federal Motor Carrier Safety Regulations mandate that front steer axle tires must have at least 4/324/32-inch tread depth in every major groove. Because the front right steer tire measured only 3/323/32 inch, it is below the legal threshold and represents an out-of-service safety violation.

Step-by-Step Solution

1
Identify regulatory tread depth thresholds by axle position.
Front steer axle tires require at least 4/324/32 inch of tread depth in every major groove, while all other tires (drive and trailer) require at least 2/322/32 inch.
Steer tires demand greater tread depth to maintain steering traction, displace water, and prevent hydroplaning.
2
Evaluate the non-steer tire measurements.
The forward outer drive axle tire (3/323/32 inch) and rear dual trailer tires (2/322/32 inch) both meet or exceed the 2/322/32-inch minimum for non-steer positions.
These measurements satisfy Federal Motor Carrier Safety Regulations for non-steering axles.
3
Evaluate the steer axle tire measurements.
The front left tire (5/325/32 inch) is compliant, but the front right tire (3/323/32 inch) falls below the mandatory 4/324/32-inch minimum threshold.
Operating a commercial vehicle with less than 4/324/32 inch of tread on any front steer tire is illegal and unsafe.

Key Concept

Tread depth regulatory standards require at least 4/324/32 inch on front steer tires and at least 2/322/32 inch on all other commercial vehicle tires.
Estimated Time:1m 30s
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