SAE J2923_201605

This Recommended Practice applies to on-road vehicles with a GVWR below 4540 kg equipped with disc brakes. This Recommended Practice is the result of an industry effort to develop inertia-dynamometer test procedures to assess brake drag under a series of speed, pressure, and temperature conditions. The test allows the project or application engineer to determine or compare the amount of brake drag for a given design level or configuration. The test provides a standard method to better quantify and better understand the parasitic (drag) torque generated by the brake corner during the off-brake condition under repeatable laboratory conditions. This inertia-dynamometer test procedure provides a method to quantify brake drag measurements combining light, moderate, and severe braking with a brake drag matrix. This matrix combines increasing static preconditioning pressure applications before measuring brake drag at increasing braking speeds. Data from this test is useful to assess the influence of certain design features, determine brake sensitivity to braking conditions, and support a comprehensive brake performance evaluation in conjunction with other measurements for pedal feel, noise, performance, and durability. Elements from this recommended practice are also applicable or useful for other laboratory test procedures to assess brake drag following standard fuel economy cycles. To better characterize the brake drag behavior of a given brake corner, include other brake drag procedures which rely more on vehicle-level evaluations. These inertia dynamometer evaluations use speed profiles and test sequences to replicate coast-down testing from proving ground testing. Due to the novelty of this Recommended Practice, the Task Force encourages users of this document to contact the SAE Staff Representative for Ground Vehicle; Motor Vehicle Council; Chassis Systems Group; Foundation Brake Steering Committee, or the Chairman of the Brake Dynamometer Standards Committee with questions and comments. This feedback will prove valuable for future revisions and updates to the Recommended Practice. The Task Force is working on developing an example of the test output to present the recommended report layout. This SAE Recommended Practice is intended as a guide towards standard practices and is subject to change to keep pace with experience and technical advances.