The most important factor to safely operating at any weight is
SPEED.
For example: A OEM (stock) Super Duty can tow 100,000 pounds safely (not legally) at a very low speed.
GVWR's & GCWR's are set by manufacturers based on all equipment components, and limited by the weakest components.
Operators of loads exceeding legal weight limitations of equipment or roadways (bridges), have the option of obtaining over weight trip permits from each state's DOT office. The over weight office will help determine safe routes for the trip.
Ex: Mobile Home transporters do this regularly. The load is "nonreducable", the axles, wheels, tires, hitches, and suspension are all overloaded. Special permits are obtained.
The FMCSA
does recognize modifications to increase vehicle GVWR & GCWR.
Some states will also regulate how modifications are to be accepted. Ie: from a licenced shop, some default directly to FMCSA with no additional requirements.
Example: A "Super Duty" truck is built from existing and fabricated materials. The "builder" will designate a GVWR for the vehicle at the time of titling. This will be the vehicle's legal maximum GVWR.
In the event of a traffic stop, state safety departments (DPS & DOT) may inspect and enforce all components of vehicles for their individual weight rating. Ie: Tires, Axles, Chassis, Drivetrain, Brakes, Hitches, Horse Power of engine, etc., and also GVWR, and GCWR.
The only way to "legally" exceed a vehicles GVWR or GCWR without special movement permits, is modification.
This is not, however, to say that the vehicle cannot be "safely" operated without meeting these requirements. Safety and Legality are two seperate, and distinct objectives.
Ex 1: An International 4900 is operated at 35,000 pounds gross weight. The equipment is designed and rated at this capacity, however, the vehicle is licenced for operation at 26,000 pounds GVW in order to avoid the FMCSA (interstate) CDL requirement for the operator. The vehicle can be safely, not legally operated at 35,000 pounds GVW.
Ex 2: A farmer licenses his F450 Super Duty for 35,000 pounds GVW. The manufacturers designated GVWR is 16,000 pounds. He pulls a load down a farm road to the market with 20,000 pounds GVW and 50,000 pounds GCW, truck and trailer. He is legally licensed to operate the vehicle, however the vehicle and it's components (OEM) are not rated for such operation, and as such he may be legally over weight and in violation.NOTE: Many rural areas permit exceeding GVWR and GCWR providing they meet certain exceptions; Ie; farm roads, etc.
It is also important to note, whether permitted or not, an operator CAN operate an overweight vehicle SAFELY, in any circumstance, providing he is competent in the operation and capabilities of the vehicle, and careful in planning safe operation over the route chosen.
EXCESSIVE SPEED IS THE NUMBER ONE CAUSE OF ACCIDENTS INVOLVING HEAVY VEHICLES.Posted safe speeds for automobiles are not necessarily safe speeds for heavy or towing vehicles.
