This code is intended for commercial vehicles over 4500 kg (10 000 lb) with brake systems having typical service pressure ranges 0 to 14.1 MPa (0 to 2050 psi) hydraulic or 0 to 830 kPa (0 to 120 psi) air and is not directly applicable to vehicles with other systems. Air over hydraulic systems are to be tested as air systems.

The code provides test procedures and instructions for: a. instrumentation and equipment; b. vehicle preparation; c. determining brake system energy absorption capacity; and d. calculation of brake rating.

The purpose of this code is to provide a method for determining a brake system rating for new commercial highway vehicles, based on the energy absorption and dissipation capacity of the brake system as established by a repeated test procedure. For performance requirements, refer to SAE J257 (FEB97).

The code includes provision for those single unit, combination, and special vehicles which cannot be loaded to the manufacturer's gross vehicle weight rating, or cannot be accelerated in the time interval required, or cannot attain the specified 80,5 km/h (50 mph) speed.

Methods for measuring energy absorption capacity, other than described herein, may be equally valid