Free-Rolling Cornering Test for Truck and Bus Tires
|Publication Date:||1 September 2015|
This SAE Recommended Practice describes a test method for determination of heavy truck (Class VI, VII, and VIII) tire force and moment properties under free-rolling cornering conditions. The steady-state properties are acquired as functions of slip angle and normal force, which are changed incrementally using a sequence specified in this document. The data are suitable for use in vehicle dynamics modeling, comparative evaluations for research and development purposes, and manufacturing quality control.
This document addresses two principal topics; a) the description of a hypothetical "Ideal Machine," and b) a standard directly applicable to testing practices currently common to the industry. The references to the "Ideal Machine" are meant to provide a roadmap for the testing machine manufacturer, providing direction and goals for the next generation of testing capabilities. The ranges of parameters for the "Ideal Machine," including those in Tables 2 and 3, are intended to represent minimal requirements to meet the full and complete data needs of the industry. The remaining documentation provides practical guidelines for the test engineer to ensure the integrity of data generated using current and conventional means.
For the purposes of this document, truck tires are defined as
being the tires mounted on all heavy commercial over-theroad trucks
and buses. Examples of vehicles which use heavy truck tires
Effects Not Considered
The effects of inclination angle and spindle torque or any combination of inclination angle or spindle torque with slip angle and / or normal force are not considered in this document.
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, the CALSPAN Tire Research Facility (TIRF), and an outdoor over-the-road dynamometer, the University of Michigan Transportation Research Institute (UMTRI) Mobile Tire Dynamometer. This document does not require a machine to match the ideal machine defined in Section 1.3.1 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 supporting data 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.
This document references an ideal machine which is capable of fully matching every item in this document, as well as those found in documents SAE J2673 and SAE J2675, to the extent specified herein. Such a machine neither existed at the time this document was written nor is it certain that the technology to build such a machine exists at this time. However, it is important to establish the parameters that define an ideal machine, so that as testing capabilities evolve, they do so with specific goals in mind. The ideal machine is defined without regard to the configuration of the machine or current capabilities - it is defined instead by its ability to provide desired levels of quality, accuracy, repeatability, and range of data.
Current limits of available technology bound the feasible performance of any type of machine to somewhat different levels. However, while the existence of an "ideal machine" would overcome these limits in performance, this recommended procedure does not depend on having an ideal machine. Useful data can be, and has been, gathered on existing machines for years. 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.