Optimized Drive Axle Design for Class 8 Tractors Equipped with New Generation Wide Base Single Tires 2009-01-2861

Manufacturers of components for heavy trucks continually seek opportunities to reduce vehicle weight and improve operating efficiency. In recent years, new generation wide-base single (NGWBS) tires, such as the Michelin XOne^®, have provided weight reductions from 70 to over 120 kg per axle and improved fuel economy when compared to standard dual tire fitments. The NGWBS tire was designed as a “bolt-on” technology that can be put directly into commercial service on existing vehicles. As an enabling technology, NGWBS tires offer even greater improvements in overall vehicle weight reduction, safety, and fuel economy by permitting adaptation of axle and suspension architecture to take advantage of the single tire geometry and operating characteristics. This paper details the development of a new heavy truck drive axle design which is specifically optimized for use with NGWBS tires. The design principles and details of component arrangement of bearings, hub, axle shaft geometry, bolt circle, and mounting rim offset are included. A physical prototype axle was constructed and installed on a 6x4 tractor for operational testing and validation. Initial results of vehicle testing with the new axle demonstrate the following:

1. i)
   additional weight savings;
2. ii)
   easier and less expensive brake system maintenance;
3. iii)
   easier adaptation of automatic tire inflation systems on the drive axle;
4. iv)
   improved tire tread life due to reductions in load-induced camber.

Finally, the authors will provide perspectives on vehicle suspension upgrades which become possible with axles designed specifically for NGWBS tires.