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Difficulty: HardTire Failure and Blowouts

If a dual tire on a drive axle suffers a sudden blowout while operating a tractor-trailer combination at highway speed, the driver should immediately activate the trailer hand brake (trolley valve) to prevent fishtailing and stabilize the vehicle.

Answer: Answer

Answer

False
The statement is false because CDL emergency protocols strictly prohibit applying any brakes immediately following a tire blowout. Activating the trailer hand brake while drive-axle traction is compromised can cause the trailer wheels to lock and initiate an unrecoverable jackknife.

Step-by-Step Solution

1
Identify the emergency condition and the proposed driver action.
The scenario involves a rear drive-axle blowout on a combination vehicle, and the proposed action is applying the trailer hand brake.
Understanding the vehicle dynamics during tire failure is essential to determine safe intervention steps.
2
Analyze the mechanical and dynamic effects of applying the trailer hand brake during drive-axle instability.
Independent trailer braking can instantly lock the trailer tires on highway surfaces, destabilizing the entire combination unit and precipitating a trailer jackknife.
Trailer hand valves should never be used in emergency braking or to control skids and tire failures.
3
Evaluate the statement against the standard CDL tire failure protocol.
The core rule across all tire blowout scenarios is to maintain a firm two-handed grip on the steering wheel, stay completely off all brakes (both foot brake and hand valve), allow the vehicle to coast down in gear, and apply gentle braking only after vehicle speed has drastically dropped.
Immediate braking during a blowout removes necessary tire traction for directional stability.

Key Concept

Tire blowout control protocol and prohibition of emergency braking
Estimated Time:1m 0s
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Topics

Tire Failure and Blowouts

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