ORIGINAL: GreaTOne_65

Highplains, I can relate to your example about the coal cars on the train pulling easier when they had coal in them. Many years ago, hauling grain to Toledo, we had a 38' trailer, behind a 318 Detroit powered Astro. When we got the trailer unloaded, the tarp blew off, so my brother and I just rolled it up and put it inside of the trailer. With a 20 ton load of grain on, the Astro would pull the load in 13th gear at 60mph, but on the return trip, with the trailer untarped, 55 was all she could muster in 12th. From then on we never pulled a trailer with out the tarp on, loaded or empty.

Just another example, of what wind drag can do.

Dale