FMVSS Inertia Dynamometer Test Procedure for Vehicles Below 4540 kg GVWR
J2784
This Recommended Practice is derived from the Federal Motor Vehicle Safety Standard 135 vehicle test protocol as a single-ended inertia-dynamometer test procedure. It measures brake output, friction material effectiveness, and corner performance in a controlled and repeatable environment. The test procedure also includes optional sections for parking brake output performance for rear brakes. It applies to brake corners from vehicles covered by the FMVSS 135 when using the appropriate brake hardware and test parameters. This procedure applies to all passenger cars and light trucks up to 3500 kg of Gross Vehicle Weight Rating.
This recommended practice is not applicable to evaluate the braking system performance of two-axle multipurpose passenger vehicles, trucks, and buses towing a trailer in combination. Reference SAE J2807 Recommended Practice for Performance Requirements for Determining Tow-Vehicle Gross Combination Weight Rating and Trailer Weight Rating.
Rationale: This revised document takes into consideration new technologies for braking systems like (a) vacuum assist, (b) electric parking brake (EPB), and (c) regenerative braking. The inertia calculation references the latest version of the SAE J2789 to calculate the test inertia, including two methods to reflect the brake blending for the regenerative braking systems. This revision also addresses formatting and grammatical corrections and clarifies items about FMVSS 105, FMVSS 135, or both. Other aspects of the rationale from previous revisions of this SAE Recommended Practice (RP) are still applicable. Lastly, this revision clarifies the scope regarding trailer towing performance and rating.
