Ask an Expert: Commercial Truck Brake Failures

Ask An Expert is a question-and-answer column designed to address common questions related to forensic investigation and property damage. Each month we’ll feature one or two questions submitted by you – our readers and customers – and provide detailed, easy-to-understand answers. Email your questions to [email protected] or submit your questions here.


How long have anti-lock braking systems been required for trailers?
Jeff Bradley, PE.: They have been required since 1998.

Other than lack of maintenance, are brake adjustments a problem?
A: Typically, not with automatic type slack adjusters. However, if the brake pad surface wears to be thinner than its minimum thickness, the S-cam can flip. This can drastically reduce the overall braking force and affect the braking performance of the truck.

Does the braking system for a single trailer hauler differ from the double trailer hauler braking system?
A: There isn’t any real difference in the braking system; however, drivers are required to have a special endorsement for a longer combination vehicle (any combination of a truck, tractor and two or more trailers or semi-trailers).

When long haul truckers travel on the highway, what do the “Check Point Stations” do?
A: Department of Transportation inspections are required annually; most check points just measure the weight of the vehicle; however, the DOT may also do an additional inspection. Inspections vary, and there are multiple levels of inspections. Examples can be found at

Is engine brake use recommended during wet conditions?
A: Engine brake use is not recommended during wet conditions for less experienced drivers.

What are some resources for checking for recalls?
A: Information about vehicle recalls can be found on the National Highway Traffic Safety Administration’s website at


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About the Expert

Mr. Jeffrey Bradley joined Donan in 2009. Mr. Bradley has prior experience in truck manufacturing, automotive repair and plumbing design. His area of expertise is automotive, and he completes a wide range of projects at Donan related to roof inspections, water intrusion, water losses and appliance failures, among others. Mr. Bradley is a licensed professional engineer in Alabama, Arkansas, Florida, Georgia, Kentucky, Mississippi, North Carolina, Pennsylvania, Tennessee and Virginia. Mr. Bradley has an Associate degree in Architectural Engineering Technology from Nashville Technical Institute and a Bachelor’s degree in Mechanical Engineering from Tennessee Technological University.

 View Jeff’s full professional profile here.


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