The introduction of Worldwide harmonized Light vehicles Test Procedures (WLTP) in Europe and increased Corporate Average Fuel Economy (CAFE) standards in the United States for fuel economy and emissions reductions are going to have a larger role in vehicle development. Two major ways to increase fuel economy and reduce emissions are by reducing mass and improving aerodynamics. In the wheel segment, these two possible means to improve fuel economy compete against each other. Most lightweight wheel designs are detrimental to aerodynamics and aerodynamic wheels are seen as unstylish and with a high mass penalty. One solution is through the use of composite wheel technology which replaces non-structural aluminum with lighter weight materials.
This study used SAE J2263 and SAE J2264 procedures to establish baseline fuel economy numbers and to evaluate various mass, inertial and aerodynamic differences between wheel concepts. Additional physical studies included steady state testing and real world road testing. Computational Fluid Dynamics (CFD) analysis was also performed to examine the link between the fuel economy differences and coefficient of drag (Cd).
It is concluded that the lightest weight wheel studied is not the most fuel efficient, nor is the heaviest. Additionally, applying a surface without a permanent attachment, such as a wheel cover, is also not the most fuel efficient. The wheel technology that provides the highest fuel efficiency and reduces emissions is one that focuses on improving aerodynamics through the use of permanently bonded aerodynamic surfaces and mass optimized structural backbones.