The aerodynamics associated with rotating tires and wheels are complicated by many factors. Drive wheel fairings mounted between and behind the drive wheels of the tractor streamline the airflow around the rotating tires and direct airflow as it leaves the tractor. They provide a net benefit to the fuel economy of the vehicle, and are often used in combination with wheel covers on the tractor for a higher net benefit. Fuel savings for these devices are estimated to be about 2%.
It is also believed that these devices improve appearance and help reduce water spray.
Due to lower drag
“We continue to update our fleet with more fuel efficient post-2014 U.S. Environmental Protection Agency emission compliant engines, install aerodynamic devices on our tractors, and equip our trailers with trailer blades, which all lead to meaningful improvement in fuel efficiency.” — Knight Transportation
“Appearance and detail of our equipment means a lot to our drivers. Drive wheel fairings don’t just save us money, but our drivers like them too.” — Brad Pinchuk, Hirschbach
“Sleeper tractor aerodynamics have been finely tuned by all OEMs. Eliminating various features can add 10% to a fleet’s fuel expense,” — Chief engineer at a major truck builder.
The Confidence Matrix has been issued to help fleets make decisions about tractor aerodynamic devices.