Roof Rack Drag Coefficient

Drag is a force that moves parallel to the airflow.

Roof rack drag coefficient.

This is because the air flows over the top of the vehicle following the smooth lines of the hood and windshield then collides with the roof rack and causes turbulence. This is because as the air flows over the top of the vehicle following the smooth lines of the hood and windshield then collides with the roof rack and causes turbulence. Use of roof racks requires vehicles to expend more energy due to aerodynamic drag. The net drag coefficient yes there s a formula for that naturally depends on your vehicle and what you re carrying but the effect on fuel economy is unequivocally negative.

While there have been studies of their impact on individual vehicles depending on the configuration the fuel consumption penalty can be 0 to 25 percent on passenger cars this is the first study to estimate impacts at the national level. According to message boards across the internet that s a rather conservative estimate. For example roof rack usage rate estimates were based on nationwide highway video surveys conducted by the authors and workers recruited through amazon mechanical turk. The drag coefficient is a measure of how easily the car moves through the air.

While roof racks are very useful in carrying extra storage on a vehicle they also increase the frontal area of the vehicle and increase the drag coefficient. Creating more drag creates more work for the car. It was a way of doing a. According to the epa a good rule of thumb is that a loaded roof rack reduces fuel economy by five percent.