Search Results

The paper has two objectives - (1) to describe the manner in which tires are involved in the “torsional nibble” disturbance an occasional problem in vehicle development, and (2) to illustrate a generally applicable approach for diagnosing the relationships between tire properties and subjective disturbances.

Engineers who are developing new models of vehicles invest considerable effort in adjusting the steering characteristics to conform with specific commercial objectives. In this process, tires have to be redesigned so that their steering properties match the requirements imposed by the physical nature of the vehicle and the subjective reactions of test drivers. One method for the identification of the underlying physical system, and the determination of the required tire properties proceeds by the general approach outlined in the paper.

The paper treats the following: a. The basic mechanical processes leading to the formation of the rolling resistance of radial ply pneumatic tires, b. Special testing procedures for elucidating the contributions and characteristics of these mechanical processes, c. An assessment of the relative contributions to the rolling resistance from various mechanisms and parts of the tire.

Disturbances transmitted to the occupants of vehicles often involve tires in their formation or transmission. Tire engineers attempting to reduce disturbances in specific vehicles have two courses of action; alter the tire design according to insight or whim until subjective testing indicates improvements; or analyze the chain of relationships from sensory impression through the tire-vehicle system to internal tire design. This paper describes a “chain-of-relationships” procedure using sensory comparison techniques for identifying pertinent physical stimuli, and an approach to system modeling that best identifies structural tire properties.

There can be no control over environmental pollution without methods for measuring how the environment is being affected by mankind. Consequently, when traffic noise was identified in 1964 by communities as an important form of pollution, it became necessary to measure the amounts of noise present and to assign relative importances to various sources in vehicular traffic. Truck tires were identified as being significant contributors and engineers from the tire and truck manufacturing industries acting under the auspices of the SAE set about to develop a test procedure that satisfied the immediate need - to initiate control over truck tire noise. This paper is a review of the outcome of that effort by one who participated in the earlier work on the testing standard. How well the method works, and how well it serves to meet the objectives now on the horizon are the preliminary topics of this discussion.

This presentation is a sequel to Paper 762035 in that an alternate method of testing for tire noise is investigated and the results of experimental studies are described. The alternate method is designed so as to preserve in the proposed measurements, the pertinence of J57a. Comparative testing of numerous tire designs in the two manners shows that this objective has indeed been accomplished. Rather than presenting the experimental details behind each of the various foundations for the proposed method, this paper confines its discussion to the items significant to the description of the method and to a comparison with the J57a procedure.

The objective of the investigation is to provide a basis for judging whether or not the dynamic steering adjustments of the tire forces affect vehicle performance in a significant manner. The differential equation of cornering force adjustment is developed from experimental data. This equation is applied, for a typical radial ply tire, to a crude but sufficient mathematical model of a vehicle. The responses of the vehicle in certain maneuvers differ to some degree when the model is programmed with instantaneously reacting tires or with simulations of actual tires. The authors judge that there are slight and unimportant effects on the path and heading curves of the vehicle due to the delays in build-up cornering force. On the other hand, there appear to be detectable effects that may be important in the sensory information provided to the driver.

The paper presents data showing the effects of the state of wear, structure, load, and inflation pressure on the cornering stiffness and aligning torque stiffness of typical passenger tires. A method is introduced and applied for assessing contributions of local elements of the tread interface to the cornering force, the cornering stiffness, the aligning torque, and the aligning stiffness. There is also a further identification of the contributions to the aligning torque from fore and aft interfacial stress distributions and from lateral stress distributions. Pneumatic trail is redefined in the light of the interfacial measurements, and values are established for various operating conditions, states of wear, and tire types.

A method is derived and confirmed for predicting the tread wear configurations of tires positioned on nondriven axles of passenger vehicles. The method is based on laboratory measurements of the interfacial stresses of freely rolling tires and takes account of perturbations in these stresses that occur during the road test procedure. Wear is found to occur primarily at the exit end of the tire-road interface, and the degree of wear is related to the interfacial pressure and slip determining conditions at that location. The steering properties of the tire also enter into the determination. Abrasion resistance of the rubber, temperature, character of the road surface, the test course, and the procedure all appear in the equations of wear in aggregate as a coefficient. In addition, there are interference effects between adjacent ribs of the tire that are established and taken into account.

This paper outlines the nature of the measuring equipment used in the investigation of tire-road interactions and presents the results of a study of the interfacial stress distributions of a radial-ply, a bias-belted, and a 4-ply bias-angle tire. There is a discussion of tractive ratios and effective coefficients of friction. Distributions of tractive ratios are displayed for all of the conditions treated and for the three types of tires. The paper also covers the changes in stress distributions that result from steering and the relation of these alterations to the lateral thrust and self-aligning torque of the tires.

The A-weighted sound level accounts for the bulk (but not all) of the jury's reaction to the sound of trucks coasting on a variety of tires. A component of the jury's reaction is related by the study to the manner in which the sound decays after the vehicle passes the point of observation. This component also appears to depend strongly on the characteristics of the sound. The jury's reaction shows two forms of distortion: end-of-scale compression and temporal drift. The analysis attempts to account for these factors and to see beyond them into the jury's basis for reacting.

As highway development programs brought increased truck traffic through formerly isolated communities, public sensitivity to truck tire noise increased significantly. Industry was alert to the possible consequences of social and legal pressures and acted in concert to set up standards for noise control and for establishing criteria by which to measure annoyance levels. Work by several leading associations provided a starting point for investigations by the SAE Truck Tire Noise Subcommittee. The Subcommittee's efforts resulted in formulation of a tire testing procedure and a consolidation of requirements to be incorporated into a proposed standard. This paper reviews the objectives and approaches of the Subcommittee and serves as an introduction to the accompanying papers.

The forces generated by tires when traveling over irregular roads are related to the structure of the tire and to the geometry of the road surface in a useful mathematical relationship. Linearity and superposition principles allow an idealized and synthetic road irregularity to represent the response of a tire to realistic kinds of road irregularities. The association of the enveloping forces with factors related to the structure of tires facilitates the understanding of the enveloping responses. The analysis of the forces for the idealized road irregularity, coupled with the Fourier integral analysis of road surfaces, produces the spectrum of outputs for exciting modes of vibration in the tire itself and in vehicles.

The paper describes the enveloping properties of truck tires as consisting of two components of force, one in the vertical direction and another in the direction of travel. The responses to irregular surfaces are mathematically accountable in terms of the response to a step in pavement elevation. Tires may therefore be readily characterized through their reactions to step functions. Curves display the differences in enveloping properties available in the 10.00–20 size on the open market.

THE standard tire will operate continuously at 94 mph without failing, but last only about 50 miles at 100 mph. This paper discusses means of counteracting the high power consumption and inertial effects that cause such deterioration of tire materials at high speeds. The authors describe one special tire with tread ground away in such a manner as to lower power consumption and allow operation at 120 mph with very little distortion. Whatever means are used to allow the higher speed operation sure to be required of future tires, the authors, say, major improvements in physical properties will account for only a few mph speed improvement. Eventual requirements, they feel, will be met with compromises in tread wear and perhaps cost.