Executive Summary

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.

Tractor Aerodynamics
What Fleets Are Saying

“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.

 

Decision Making Tools

The Confidence Matrix has been issued to help fleets make decisions about tractor aerodynamic devices.

Decision-Making Tools

Conclusions
  • Fleets should use the standard, optimized aerodynamic packages developed by tractor manufacturers. 
  • Fuel efficiency can be lowered by about 10% by moving to partial or no aerodynamics.
  • Tractor and trailer ride heights should be matched for as many miles driven as possible.
  • Fleets operating day-cab tractors should pursue greater adoption of tractor aerodynamics.
  • Tractor manufacturers should design and make available aerodynamic features for day-cab tractors including those powered by natural gas.
  • Future EPA and NHTSA Greenhouse Gas Regulations will continue to challenge tractor builders to improve the aerodynamic drag of these vehicles.
Manufacturers
  • Flow Below