This Recommended Practice provides a road test procedure for trucks and buses, to evaluate their compliance with Federal Motor Vehicle Safety Standard (FMVSS) 121; Air Brake Systems. Units of measure are English in lieu of metric to be consistent with FMVSS 121.
This SAE Recommended Practice is intended as a guide toward industry practice and subject to change so as to keep pace with experience and technical advances. The usage of this recommend practice is limited to trucks and buses equipped with air brake systems with a GVWR greater than 10000 pound.
This document has been modified from SAE J1626-1 truck tractor to incorporate air brake equipped trucks and buses test procedure. The following sections were modified; changed all truck tractor wording to trucks and buses throughout the document, 3.1 definitions add trucks and buses, 3.5 was removed based on combination weight not applicable, 3.7.1 was removed based on tractor trailer combination not applicable and modified for trucks and buses, 3.13 remove unbraked control trailer not applicable, 6.8 removed control trailer reservoir not applicable, 6.13 and 8.2.2 removed the additional brake adjustment at the completion of the 500 snub burnish not applicable with trucks and buses, 7.0 test sequence was modified to follow FMVSS 121 truck and bus sequence, 8.1.3 truck and bus loading changes, 9.1.3, 10.1.2 and 11.1.2 removed brake adjustments not applicable, 9.1.1 corrected 20 foot cone spacing, 9.2.1 changed 35 to 30 mph and changed 44 to 40 mph, 9.2.2 corrected reference 3.9 to 3.8, 11.2.1a removed the word ‘only’, Figure 5D removed LLVW, and corrected all header spacing between 2 digit section number and header. Figures (Data Sheets) removed trailer ballast C.G. height measurement, bobtail proportional and fifth wheel height not applicable.