SAE J3211_202512

The SAE J3211 procedure applies to squeal evaluation for foundation brakes using single-ended inertia dynamometers for friction couples used on vehicles with regenerative braking systems. This document applies to squeal noise occurrences for on-road passenger cars and light trucks with a gross vehicle weight rating of 4536 kg or below and with at least one rechargeable energy storage system as a source for propulsion. The procedure incorporates aspects related to (a) minimum inertia dynamometer capabilities, (b) fixture requirements and setup, and (c) test sequences with emphasis on brake temperatures, brake pressure profiles, and strategies to represent brake blending. For this document, squeal occurs when the peak noise level is at least 70 dB(A) between 1.25 and 16 kHz for tests using full suspension corners or complete axle assemblies, or between 2 and 16 kHz for brakes not using an entire suspension corner. Test facilities intending to use this document, building on their expertise in conducting SAE J2521, shall review in detail the changes to test parameters (mainly brake temperatures and brake pressures) for legacy modules. This document also applies to vehicles with electromechanical braking systems to actuate the foundation brake. The test requester and the test facility are responsible for converting the hydraulic pressure levels into their equivalent clamping forces for brakes using electromechanical actuation. Before using this document for chassis dynamometer testing, review in detail the specifics related to at least (a) instrumentation, including in-cabin microphones; (b) threshold levels for noise detection; (c) temperature control priority between the front and rear axles; (d) vehicle loading and load distribution; (e) cooling air and environmental conditioning; (f) detailed terminology and labeling of channels and sensors; and (g) the regenerative settings and the state of charge during the test. Before using this document along with other methods to recreate the regenerative brake blending (e.g., Software-in-the-Loop or Hardware-in-the-Loop), consider (a) the vehicle powertrain, blending architecture and its applicable models, (b) actual profiles intended to recreate (e.g., control strategies, state of charge, test scenarios), and (c) actual embodiment of the simulation and integration with the native controls of the brake dynamometer. This document does not include noise from other sources (e.g., parking brakes, electric machines, driveline components). Foundation brakes used on hybrid and electric vehicles (EVs) with regenerative (regen) braking tend to have lower average operating temperatures than vehicles using internal combustion engines. Besides, the intervention of the foundation brakes during vehicle deceleration is a function of the blending technology and the capabilities of the propulsion system. Some vehicles can achieve a high percentile of decelerations during regular vehicle use using only the regenerative system with minimal foundation brake intervention. Lastly, there is a lack of engine noise, a high percentage of hybrid and electric vehicles operating in cold weather, and some electric vehicles with high-performance capabilities that demand a new approach to measure and characterize brake squeals. This document addresses multiple aspects of brake squeal for regenerative braking systems by (a) focusing on lower operating brake temperatures also induced by more extended periods between wheel brake events, (b) reducing the brake pressures for several modules (including burnish), and (c) defining test sequences and brake profiles applicable to regenerative braking systems.