The three areas of concern when employing tractor aerodynamics are: the tractor-trailer spacing, the tractor-trailer height differential, and the occurrences of crosswinds during normal operation. Spacing beyond 18" will allow air to spill down into the gap, trailers that are higher than the tractor deflector will create a point if interruption in airflow, and crosswinds will bypass the tractor and directly hit the trailer. In order to get the most from your tractor aerodynamics tractor-trailer spacing should be no more than 24", the height of the two should be equal, and cab extenders will help prevent crosswinds from making direct contact with the trailer—or, you can eliminate these uncertainties by applying Nose Cone to the trailer.