Interesting.
I am not a mechanical engineer (rather Electro-Optical) but I have worked on a lot of mechanical hardware in the design and implementation stage during my 44 year aerospace engineering career. To the best of my recollection most if not all of the mechanical items that I encountered were designed and tested with load margins of at least 150% and if critical 200% of rated load. Indeed design margin was required and is standard engineering practice (even in Optical design). I would be very surprised, shocked actually, if the GVWR on vehicles was based on only 100% load design or testing with no margin.
I did a google search to see if I could find any info on truck manufacturer design margins for weight ratings and all I found is that axles often have margin built into their ratings to ensure they do not fail.
I did find the following relative to larger trucks (however, I suspect this also applies s to light duty trucks):
"Often, GVWR and gross vehicle weight (GVW) are thought to be the same, but they are not. A truck’s GVWR is the maximum weight rating established by the chassis manufacturer. GVW is the total weight of the truck and payload at a point in time.
There’s a common misconception that a truck’s GVWR is determined by adding gross axle weight ratings (GAWRs) together for all axles. Although this was a common way of calculating GVWR many years ago, it’s no longer an accurate method.
The chassis manufacturer task of establishing a vehicle GVWR is much more difficult today due to advancement of safety system standards and how vehicles meet these requirements. This is why many trucks have a GVWR much lower than the combined axle ratings. It’s not uncommon for a truck with a GVWR of 19,500 pounds to have a front axle rated at 7,500 pounds and a rear axle rated at 14,700 pounds.
Safety standards that apply to braking, vehicle stability, and chassis manufacturer internal standards for durability, dynamic stability and handling can restrict GVWR even though the sum of the axle ratings exceeds 22,000 pounds. In this instance, the OEM set the GVWR at 19,500 pounds based on test results and vehicle dynamic performance to ensure a safe, reliable truck.
A specific vehicle’s GCWR is based on parameters established by chassis manufacturers. The manufacturer makes an assessment in accordance with SAE International test protocols, determining maximum GCWR. Additionally, the OEM runs stringent tests based on internal requirements which may include testing total GCWR braking capability using only the towing vehicle chassis braking system. GCWR is the total weight of the truck pulling the trailer and the trailer itself. The truck chassis dictates proper GCWR for safe operation of the combination truck and trailer."
https://www.ntea.com/NTEA/Member_benefits/Industry_leading_news/NTEANewsarticles/The_role_of_GVWR_and_GCWR_in_specifying_work_trucks1.aspx
SAE J2807_202002 Performance Requirements for Determining Tow-Vehicle Gross Combination Weight Rating and Trailer Weight Rating establishes minimum performance criteria at GCWR and calculation methodology to determine tow-vehicle TWR for passenger cars, multipurpose passenger vehicles, and trucks. This includes all vehicles up to 14000 pounds GVWR. This is a document that requires purchase so I cannot see the contents.
In absence of evidence to the contrary, I am confident vehicle manufacturers have margin in their designs and we can rely on the GVWR ratings of our trucks to determine safe loads. If this were not the case I suspect the potential liability to the manufacturers would be measured in very large dollar amounts.
I respect your opinion for the use of your truck but relative to a recommendation to others I think it errs on the far too cautious side.
If anyone reading is intimate with truck manufacturer design rules and design margins It would be most helpful to learn if there are standard practices or design rules relative to GVWR margin.
I hope this is helpful,
Craig
