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Difficulty: HardTires, Wheels, and Rims Inspection

A commercial motor vehicle driver conducts a pre-trip inspection on a straight truck and measures tread depths and physical clearances across all wheel assemblies. Which of the following findings fully complies with commercial vehicle safety standards and allows the truck to be operated legally?

  1. A
    A steer axle tire displaying a uniform tread depth of 332\frac{3}{32} inch across all major circumferential grooves with no fabric exposed.
  2. A drive axle tire displaying a remaining tread depth of 332\frac{3}{32} inch across all major grooves with no ply or cord exposed.Answer
  3. C
    A drive axle dual assembly where both tires measure 432\frac{4}{32} inch of tread depth, but their inner sidewalls make continuous contact under load.
  4. D
    A non-steer tire displaying 332\frac{3}{32} inch of tread depth in the center groove but worn down to 132\frac{1}{32} inch in one major outer groove.

Answer

A drive axle tire displaying a remaining tread depth of 332\frac{3}{32} inch across all major grooves with no ply or cord exposed.
Federal commercial motor vehicle safety regulations require a minimum tread depth of 232\frac{2}{32} inch in every major groove on all non-steer tires (including drive and trailer axles). A drive tire with 332\frac{3}{32} inch of sound tread across all major grooves and no exposed cord exceeds this requirement and is completely legal for operation.

Step-by-Step Solution

1
Identify regulatory tread depth thresholds by axle position.
Front steer axle tires require at least 432\frac{4}{32} inch (4/32 in4/32\text{ in}) in every major groove, whereas non-steer tires (drive and trailer) require at least 232\frac{2}{32} inch (2/32 in2/32\text{ in}) in every major groove.
Federal CDL safety regulations establish distinct minimum depth limits depending on whether the tire controls steering or supports drive/load axles.
2
Evaluate mechanical clearances and physical condition rules for dual assemblies.
Dual tires must not touch each other or any vehicle component, and no major groove on any tire may fall below its respective axle threshold.
Direct contact between dual tires creates catastrophic heat through friction, and uneven wear below legal limits compromises vehicle traction and water evacuation.
3
Select the condition that completely satisfies all regulatory criteria.
A drive axle tire with 332\frac{3}{32} inch across all major grooves exceeds the required 232-inch\frac{2}{32}\text{-inch} minimum and has no physical defects.
This condition meets all statutory safety standards for roadworthiness.

Key Concept

Commercial Motor Vehicle Tire Tread Depth and Dual Clearance Standards
Estimated Time:1m 30s
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Topics

Tires, Wheels, and Rims Inspection

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