Search Results

Accurate, real-world determination of tire force and moment properties is essential for computer modeling of vehicle handling. Characterizing these properties on surfaces ranging from dry pavement to snow to ice presents significant challenges. This paper reviews recent progress and results in this area for light truck tires using a test vehicle custom-designed for this purpose. It provides examples for free-rolling cornering, straight-line acceleration / braking and acceleration / braking in turns. The discussion then turns to the question of adapting the technology used to characterizing of tires for Class 8 vehicles.

The free-rolling cornering, straight-line braking, and pull force properties of a small sample of tire specifications is examined. This is done to examine potential differences between the specifications and the statistics of force and moment measurements. Two steer axle specifications, two drive axle specifications, and a trailer specification are considered, In addition, the evolution of properties for one drive axle specification is followed from new to naturally worn-out to retreaded. The summarized data is available from SAE Cooperative Research on electronic media.

The slip circle, COMBINATOR, model was developed to predict combined driving or braking and cornering performance of tires from straight-line torqued data and free-rolling cornering data only. In the original COMBINATOR paper, limited verification was presented. In the current paper, the model is shown to be broadly applicable to tires of all types. This is demonstrated through successful modeling of heavy-duty tires as large as 425/65R22.5 and by modeling of racing tires. The heavy duty tire models and summarized data are available from SAE Cooperative Research on electronic media.

A Paper-Tire is a virtual product defined as a set of force and moment equations that are entirely determined by well defined and widely recognized tire characteristics (such as cornering stiffness, peak location, and slide/peak ratio). The vehicle dynamicist may use the Paper-Tire concept to study the effects of tires with various hypothetical characteristics on vehicle behavior. If the dynamicist discovers a set of characteristics yielding a desired vehicle response, he could then ask tire manufacturers to attempt to develop a tire specification with the preferred characteristics. (There is, of course, no guarantee that tire manufacturers can develop a practical tire with the preferred characteristics.) The paper explains the general principles of the Paper-Tire concept with the help of the BNPS model (derived from the ‘Magic Formula’). A limited set of examples for tire cornering and braking performance are provided at a single load; further possible developments are indicated.

The traction effects of water depth, speed, tread wear, inflation, and load on typical 295/75R22.5 truck tires have been examined in a set of designed experiments conducted on a single pavement. The results have been typified in terms of regression models of aligning moment and lateral force at 4 degrees slip angle plus peak longitudinal force and longitudinal force at slide during braking. The effects of the principal parameters are catalogued. An approximate idea of the effect of the operational and tread wear state parameters on the ability to control vehicle motion is provided within the discussion.

The objective was derivation of a tire braking/cornering force model based on only a few standard tests, so that elaborate testing of all possible combinations of lateral and longitudinal forces could be avoided Such a model would be particularly useful for truck and bus tires because testing large tires is expensive and appropriate testing facilities are rare The required model can be derived from the concept of the slip circle (not a friction force circle) Using the slip circle concept, all tire forces at any cornering/braking combination can be predicted from the results of only two basic tests -- a free-rolling cornering test and straight-line braking test The slip circle concept has been incorporated into a subroutine called the COMBINATOR -- a piece of public domain software sponsored by SAE Cooperative Research This paper discusses the Slip Circle Model, introduces the COMBINATOR, and demonstrates effectiveness by comparison of modeling results and experimental data

The “Magic Formula” concept is an elegant, empirical method of fitting tire data for inclusion in vehicle dynamics models. Its behavior as a function of parameter values is explained in detail in this paper. This paper presents the BNPS model, a modification of the Magic Formula concept, which has been fully automated on a personal computer. This allows the ready reduction of data into practical Magic Formula type models without any investment of engineering time. BNPS fitting example results are presented.