Stop in for a cup of coffee

360DartGT66 said
... which is sorta what I was getting at ...

simply an arbitrary number now adays. However, when the thing started it was to tie it to its total towing capacity counting its own weight.

IE:

1500= Towing + GVWR (gross vehicle weight rating) =15,000 pound
2500= Towing + GWVR =25,000 pound
3500=Towing + GWVR = 35,000 pound