Inertia Dynamometer Rotor Crack Test Procedure for Air Disc Brakes


This Recommended Practice applies to air disc brakes fitted in commercial vehicles with a Gross Axle Weight Rating of 4536.0 kg or above.


Brake rotor cracks on commercial vehicles equipped with air-disc brakes which can compromise the structural integrity of the foundation brake can lead to significant maintenance and downtime costs. In order to provide an early assessment of this failure mode, vehicle manufacturers as well as brake suppliers have developed over the years multiple laboratory test procedures. These procedures determine (using different test methods and test approaches) the propensity of a given friction couple (brake rotor and friction material) to develop cracks which can render the brake out-of-service. It is the objective of this Recommended Practice to establish a uniform and industry-endorsed laboratory method which reflects the most commonly used inertia dynamometer test procedure, harmonize the test conditions when applicable, and determine the minimum requirements for the test system used to conduct the test. This Recommended Practice also presents the method and criteria to assess a rotor crack and quantify its significance when comparing test results to a baseline, a product specification, or a legacy product design.

  • SAE J 3080
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