This SAE Recommended Practice describes a test method for determination of heavy truck (Class VI, VII, and VIII) tire force and moment properties under straight-line braking conditions. The properties are acquired as functions of normal force and slip ratio using a sequence specified in this practice. At each normal force increment, the slip ratio is continually changed by application of a braking torque ramp. The data are suitable for use in vehicle dynamics modeling, comparative evaluations for research and development purposes, and manufacturing quality control.

Truck Tires

For the purposes of this document, truck tires are defined as being the tires mounted on all heavy commercial over-the-road trucks and buses. Examples of vehicles, which use heavy truck tires include: tractor/semi-trailer combinations, dump trucks, school buses, etc. Tires mounted on other types of lighter GVWR vehicles are explicitly excluded from consideration in this document.

Control Modes and Effects Not Considered

The effects of non-zero inclination angle and non-zero slip angle or any combination of non-zero inclination angle, non-zero slip angle, and spindle torque with normal force are not considered.

Test Machines

This document is test machine neutral. It may be applied using any type of test machine capable of fulfilling the requirements stated in this document. By way of example, specific data used in support of various parts of this document came from both an indoor flat-belt type machine and outdoor over-the-road dynamometer. This document does not require a machine to match the ideal machine, but does require that a test machine's performance be fully defined over its range of application. In this document, an ideal is a goal not a requirement.

IDEAL MACHINE

An ideal machine is a machine, which is capable of fully matching every item in this document, SAE J2429, and SAE J2675. Such a machine neither exists at the time this document was written nor is it certain that the technology to build such a machine exists at this time.