A vehicles GVWR is not generally limited by any one physical attribute since the individual GAWRs almost always exceed the stated vehicle GVWR to allow for loading variances. A vehicles GVWR is mainly set by the strict FMVSS safety braking performance certification and that's whyt the GVWR is always listed on that sticker on the driver's side door label. Thus according to the Federal government if you exceed the GVWR then you are no longer operating that vehicle in conformance with the federally mandated safety standards. It is extremely expensive to run and document a vehicle thru the federally mandated braking performance protocals and get it thru all the hoops to have it certified for a particular vehicle GVWR. Of course the other major factor that is GVWR is how the vehicle is classified and what other general FMVSS standards it has to meet or what classification that GVWR makes it. One area I'm not sure of is say you test and get for example an F-350 certified for a GVWR of 14,000 can you sticker it at say 9,500 (for state registrations/taxing purposes), w/o tested that same exact vehicle at that second 9,500 GVWR??? ... that I don't know and never asked the brake expert I got most of my other info on this from.
Of course then it really gets complicated when you hook a towed vehicle up since no that combo is surely over the GVWR of just the vehicle alone and while a lot of trailers have brakes what happens when you hook one of say these 2K trailers that don't require brakes up to a vehicle that is say already within 500lbs of it's door sticker GVWR???????. Now you have a vehicle with a certified braking system of say 10,000lbs that weighs 9500 by itself, but is trying to stop a total weight of 11,500 lbs clearly 1,500 lbs over the 10 certified braking performance????
Larry
