The skeptic in me is why is the same rig with a 3.42 gear set safe to say 20K gcwr, but a 3.73 to 22K, and 4.10 to 24K? Reality from a safety stand point, ie from if you hit me, kill me, I am just as dead with you hitting me at 20K as if you hit me at 24K lbs. The issue from a tow rating, is can you get a rig going on a given hill % grade at said 20 vs 22 vs 24K lbs. If this amount is say 15%, but you are going up 20% grades at the rated gcwr, you will stall out! Said rig for YOUR use, should not be rated to that wt amount, it should have been less.
Or it could be speed achieved on a 6% freeway grade, ie over 45 mph. BUT, some things that can vary this, ie frontal area. Many ratings do not include this factor, or if they do, they do not include it in the rating. Some frontal areas can pull easier than not. Compare an airstream TT to a typical fleetwood. Aluminum sided trailer, whiles lighter, need more HP to pull them down the road vs a smooth fiberglass trailer. A no slide front bedroom 5W will pull easier than a FB slide setup, which pulls easier believe it or not vs a TT.
What you can pull, safe or sanely for that matter, does not always fall upon a Weight rating. There is more than one way to figure out what a rig is rated to or should be, based on the end user.
I've also had no issues pulling over gvwr or max trailer rating. I might be a bit slower than if under.....but not always.
marty
