This Recommended Practice provides a road test procedure for truck-tractors, 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 series of SAE Recommended Practices have been developed by the Truck and Bus Vehicle Deceleration and Stability Subcommittee combined with the Brake Systems Subcommittee sponsored by the Brake Committee. These SAE Recommended Practices are intended as a guide toward industry practice and are subject to change so as to keep pace with experience and technical advances. The usage of these recommended practices are limited to vehicles equipped with air brake systems and hydraulic brake vehicles with a GVWR greater than 10, 000 lbs.
The current SAE J1626 included air and hydraulic type brake vehicle test procedures combined in one document. With the complexity of this document as combined, it was determined to better serve our industry that the subcommittee should rewrite this document into separate procedures.
As described in the parent document, SAE J1626, there are a minimum of five documents required for air- and hydraulicbraked vehicles noted below in the References Section. This procedure addresses the truck-tractor air brake combination vehicle. In summary, the following changes were addressed;
- a. Scope -separated this document into the truck-tractor procedure
- b. References - added the new separate procedure numbers and included other new references as appropriate including SAE J360 (Truck and Bus Grade Parking Performance Test Procedure) and SAE J1729 (Parking Brake Drawbar Pull Test Procedure.
- c. Test Conditions - snub burnish conditioning procedure will be conducted with the transmission in gear. This was a procedure change. Included brake adjustment clarification and recommended intervals.
- d. Test Sequence - this was revised to follow FMVSS 121 truck-tractor test sequence.
- e. Test Procedures - included maximum braking speed test to the stability and controls test. An optional test was added to initiate additional stops at a fully exhausted reservoir pressure at or near 0 psi during the failed system reservoir stops.
- f. Data Sheets - added the procedure changes and updates as appropriate for clarification.