Originally Posted by DriVer
An air dam on the front of the vehicle creates a low pressure area under the front of the vehicle and cleans up the parasitic drag from much of the front suspension gear.
I have one of those on my rig.
The mud flap located on the back of the rig downstream in the air flow will have negligible effect on aerodynamics of a large Class 6 self propelled RV.
Seeing as we are playing with a object that has the arodynamics of a large sheet of plywood, I'd like to offer a few thoughts.
A airdam on the front may affect cooling if a FRED. A large, full body width rear flap, may jam more fresh air to assist cooling of a rear engine rig.
Just things to ponder. lol