5th Wheel Settings
The fifth wheel works in conjunction with the king pin to connect the tractor to the trailer and determine the gap between the two. Some fleets are limiting the travel of sliding fifth wheels to limit the gap when the trailer is in the most rearward position.
There are a number of options for reducing trailer drive height, which can reduce overall drag through the reduction in the profile of the vehicle. Combinations of tire choices and reduced fifth wheel settings can drop the overall trailer roof height.
The biggest influence on drag is the overall frontal area of the vehicle going through the air. Minimizing the fifth wheel height keeps the trailer lower than it otherwise would be, decreasing drag. This effectively lowers the overall height of the vehicle.
Benefits
Fuel Savings (If Coupled with Higher Capacity and Higher Voltage Electrical System)
Challenges
Not Available for Most Vehicles as of March 2017
Increased Complexity of Electrical System
Higher Electrical System Voltage and Power Output Required
Reliability Issues
Increased Maintenance Costs