A fleet safety officer reviews mechanical inspection reports for several commercial motor … — Commercial Driver's License (CDL) General Knowledge Exam

A fleet safety officer reviews mechanical inspection reports for several commercial motor vehicles prior to daily dispatch. Which of the following recorded tire and wheel conditions meets all federal safety standards and is legally compliant for operation?

A
A front steer axle tire exhibiting an evenly worn tread depth of $3/32\text{-inch}$ across all major circumference grooves on an undamaged disc wheel
B
A trailer wheel assembly featuring a professionally welded repair across a previous hairline stress fracture between two stud holes
A drive axle dual tire set with $3/32\text{-inch}$ tread depth in all major grooves that maintains physical separation without sidewall contactAnswer
D
A tandem drive axle dual tire pair with $6/32\text{-inch}$ tread depth where the inner and outer sidewalls lightly press together under normal payload

Answer

The drive axle dual tire set with

3/32\text{-inch}

tread depth in all major grooves that maintains physical separation without sidewall contact is fully compliant.

Federal regulations mandate a minimum tread depth of

2/32\text{-inch}

on all non-steer tires (drive and trailer axles), and dual tires must maintain sufficient clearance to prevent rubbing. A drive axle tire with

3/32\text{-inch}

of tread exceeds the legal minimum, and maintaining physical separation ensures safe, compliant operation.

Step-by-Step Solution

Evaluate minimum tread depth requirements by axle position.

Steer axle tires require at least

4/32\text{-inch}

of tread depth, while all other tires (drive and trailer axles) require at least

2/32\text{-inch}

in every major groove.

Commercial vehicle safety regulations enforce stricter tread depth thresholds on steering axles to ensure directional control and prevent hydroplaning.

Inspect wheel rim integrity and dual assembly spacing standards.

Welded repairs on wheel rims are illegal, and dual tires must never touch each other.

Welded rims are structurally compromised and prone to catastrophic failure, while contacting dual tires cause destructive frictional heat buildup.

Identify the wheel and tire assembly that satisfies all regulatory safety criteria.

A drive axle dual tire with

3/32\text{-inch}

tread depth exceeds the

2/32\text{-inch}

non-steer minimum and, having no sidewall contact, is fully legal.

The assembly complies with all axle-specific tread depth rules and physical clearance requirements.

Key Concept

Tire tread depth thresholds and wheel mounting safety standards

Estimated Time:2m 0s

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Step-by-Step Solution

Key Concept

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