This SAE Recommended Practice describes a test method for determination of heavy truck (Class VI, VII, and VIII) tire force and moment properties under combined cornering and braking conditions. The properties are acquired as functions of slip angle, normal force, and slip ratio. Slip angle and normal force are changed incrementally using a sequence specified in this document. At each 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.

Effects Not Considered

The effects of inclination angle or any combination of inclination with slip angle, torque, and normal force are not considered in this document.

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.

NOTE: The UMTRI Mobile Tire Dynamometer was decommissioned and is no longer available in response to an institute decision to no longer engage in testing. It is still mentioned in this revision because much of the backup data for J2675 was taken with the UMTRI machine and experience with it shows the quality of information that can be obtained with a machine of this type.

Ideal Machine

This document references an ideal machine which is capable of fully matching every item in this document, J2429, and J2673. 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. However, this recommended procedure does not depend on having an ideal machine. Useful data can be, and has been gathered on existing machines. However, for repeatability, and for situations when data from different machines might be compared, it is important to document the capability of each machine that contributes data.