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This IR defines a general taxonomy (classification) of the most common fixture designs. This IR provides guidelines for design, fabrication, and installation to improve the way tests repeat, reproduce, and correlate to vehicle conditions. The different types of fixtures in this IR (including their preloading) apply to single-ended brake inertia dynamometer NVH testing, with a frequency range between 1.25 kHz and 16 kHz (per SAE J2521). This IR applies to passenger car and light trucks with a gross vehicle weight rating of 4536 kg or below. This IR does not address other sources of variability such as (a) test procedure itself, (b) environmental conditions, (c) dynamometer design, including its NVH test chamber, (d) data collection and data analysis methods, and (e) part-to-part, batch-to-batch, and design-level variation for brake and suspension hardware.

This procedure is applicable to brake pad modes between 500 Hz and 16 kHz. The parameters measured with this procedure are defined as the first three natural frequencies, fn (n = 1, 2, 3), and the corresponding loss factors, η.

This procedure is applicable to brake pad modes between 500 Hz. and 16 kHz. The parameters measured with this procedure are defined as the first three natural frequencies, fn (n=1, 2, 3), and the corresponding loss factors, η.

The SAEJ2521 procedure is applicable to high frequency squeal type noise occurrences for passenger car and light truck type vehicles that are used under conventional operating conditions. The procedure incorporates high temperature and low temperature test matrices, but does not fully account for the effects of the environment on brake squeal. Much research is currently underway in this area and can potentially be incorporated in future revisions. SAEJ2521 procedure is applicable to high frequency squeal type noise occurrences for passenger car and light truck type vehicles that are used under conventional operating conditions. For the purposes of this test procedure, squeal is defined as occurring between 900 and 17,000 Hz for disc brake tests utilizing a full suspension corner assembly, between 2000 and 17,000 Hz for disc brakes not utilizing a full suspension corner assembly and between 500 and 17,000 Hz for drum brakes.

The SAE J2521 procedure applies to high-frequency squeal noise occurrences for on-road passenger cars and light trucks below 4540 kg of GVWR. The procedure incorporates high-temperature and low-temperature test matrixes but does not fully account for the effects of the environment on brake squeal. For this test procedure, squeal occurs when the peak noise level is at least 70 dB(A) between 1.25 kHz and 16 kHz for tests using full suspension corners or full axle assemblies or between 2 kHz and 16 kHz for brakes not using a full suspension corner. Before using this recommended practice 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, and (f) detailed nomenclature and labeling of channels and sensors.