SAE J3231_202206

This SAE Recommend Practice specifies a method for measuring the deflection of friction materials and disc brake pad assemblies in a manner more consistent with classical material compressive strain testing. This SAE test method differs from SAE J2468 in the preload and maximum load applied to the test sample when deflection is measured. It adopts the material applied stress levels found in ISO 6310 (0.5 to 8.0 MPa) using a 25 mm diameter flat plunger. Legacy test methods to measure the deflection under a load of friction materials use destructive sampling to control the measurement using a known stress load. This SAE Recommend Practice addresses the brake pad deflection characteristics similar to SAE J2468, with the following refinements: Use of a 25 mm diameter flat plunger to apply stress on the brake pad material applied stress between 0.5 MPa and 8.0 MPa. Use of graphical and tabular formats to summarize and present the test results. Inclusion of guidelines to improve the accuracy and repeatability of the test method. Use of the complete brake pad assembly without the need to cut segment for testing. The deflection characteristics of friction materials and disc brake pad assemblies are commonly used in caliper and brake system design, as well as for quality control during manufacturing. Pad deflection influences many design characteristics, including brake fluid consumption, caliper stiffness and mass, caliper piston retraction, and park brake adjustment. The deflection also influences performance characteristics including brake pedal travel, brake drag, park brake performance, and the propensity of the brake system to generate noise and roughness.