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Majority of the tractor/semi-trailers are equipped with non-steerable solid trailer axles. In low speed cornering maneuvers, the trailer tires scrub in opposite directions, generating unnecessary tire wear. Steerable-axle trailers are beginning to appear in the commercial vehicle market to improve maneuverability and treadwear. In this paper, tire slip characteristics of traditional three-axle trailers in turning maneuvers are investigated analytically. Trailer-axle steer laws, defined as a relation between tractor/trailer articulation angle and trailer axle steer angle, are derived for each trailer configuration. The objective is to minimize tire scrub in low speed turning maneuvers and to generate even treadwear for different wheel positions. Effect of the vehicle forward speed on steer laws is discussed. The steer laws are further evaluated using multi-body vehicle dynamic simulation models.

Multi body simulation of agricultural vehicles such as tractors has relied on the representation of tires by equivalent spring-damper combinations. Historically, the stiffnesses assigned to various modes of deflection have been established on the basis of tests on a limited population of tires. Vehicle accelerations obtained by simulations of transport over typical terrain and rectangular obstacles using these parametric characterizations have deviated significantly from measurements. This paper reports on an attempt to develop finite element tire models, which are capable of generating quasi-static spindle forces and moments for prescribed displacements over irregular terrain and capture phenomena such as enveloping of obstacles. Though based on the tire manufacturers knowledge of constructional details, they are presented as ‘black boxes’ to the vehicle analyst for imposition of boundary conditions and loads, including inflation pressures.

Radial tires now approach 80% of the North American commercial tire business due to superior treadwear and fuel economy. One of the last areas for radial tire market penetration is the city bus market. A radial tire is less tolerant of high brake heat temperatures because: 1. There is less rubber and reinforcement bulk than a bias tire to act as an insulator in the bead area. 2. The steel ply is a good heat conductor. 3. High sulfur compounds are required for good wire adhesion and these compounds are susceptible to heat degradation. Radial tires are developed to withstand a maximum continuous running temperature of 90 degrees C. Exceeding this temperature for short periods causes no problem; however, longer exposure may cause a loss of material component strength. Therefore, it is important to know the heat flow characteristics between a brake drum and the tire. In this paper, various drum-bead heat studies will be discussed.

A mobile test station has demonstrated its effectiveness in measuring straight-ahead traction coefficients of truck tires. This system - incorporated into a modified trailer-tractor combination - is designed to test the entire range of light-truck and heavy-truck tires now in production. The tire carriage assembly is installed in the center of the flat-bed trailer. The tire is hydraulically loaded to the ground through an opening in the bed. To ensure reasonably valid tire-traction data, the system is designed to minimize variations in such test parameters as load, brake line pressure, vehicle speed, and tire orientation. The mobility of the system makes it possible to test tires on various types of road surfaces, thus providing a complete spectrum of surface coefficients for both wet and dry conditions.