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Question

Difficulty: HardSuspension System Inspection

A commercial motor vehicle with a single fractured main leaf in a multi-leaf front steer axle spring assembly must be placed out of service immediately, regardless of whether the cumulative 25 percent threshold for total broken spring leaves is met.

Answer: Answer

Answer

True. A fractured main leaf compromises axle alignment and attachment, making it an immediate out-of-service violation regardless of the overall percentage of broken leaves in the assembly.
The statement is true because commercial motor vehicle safety regulations mandate that any fracture in a main leaf—or any leaf directly securing the axle assembly to the vehicle frame—constitutes an immediate out-of-service condition. While secondary leaf spring fractures are evaluated against a 25 percent cumulative pack threshold, main leaves maintain vital axle alignment and steering control, allowing zero tolerance for structural cracks.

Step-by-Step Solution

1
Identify the specific component, axle location, and mechanical defect presented in the scenario.
A single fractured main leaf located on a multi-leaf front steer axle suspension assembly.
The main leaf is the primary structural member housing the spring eyes that anchor the axle assembly to the chassis hangers.
2
Analyze the defect against Commercial Vehicle Safety Alliance (CVSA) and Federal Motor Carrier Safety Administration (FMCSA) Out-of-Service criteria.
Any crack, break, or missing section in a main leaf is an automatic Out-of-Service violation, superseding general percentage-based rules.
Main leaf failure can cause immediate axle shifting or detachment, leading to catastrophic loss of directional steering control.
3
Evaluate the validity of the regulatory statement.
The statement correctly distinguishes between the zero-tolerance standard for main leaves and the 25 percent rule for secondary leaves.
The vehicle cannot legally or safely remain in service with a compromised main leaf.

Key Concept

Out-of-Service criteria for leaf spring assemblies and main leaf structural integrity
Estimated Time:1m 30s
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Topics

Suspension System Inspection

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