motorsports wrote:
FYI> Truck ratings are not all about axles and springs, they're about brake capacities too.
That is not true with regard to payload ratings. A DRW 1-ton tops out at 6,000 lbs. of load in the bed but the trucks brakes are designed to handle the GCWR of the truck which is considerably greater. This is covered in the SAE J2807 test practice for vehicles. This is also reflected in the increases in braking capacity that have paralleled the increases in towing capacity over the past 20 years during which time the payload capacity of trucks has increased very little if at all.
Take a look at the specs for a heavy duty pickup truck with too low a load rating to handle a camper (as noted in the glovebox) and one rated for 2500 lbs., another rated for 4,000 lbs. and another rated at 6,000 lbs. and see what is different. All that is different is the space available for passengers in the cab, the leaf springs provided, and the tires provided, with 4 tires at the rear axle handling more of a load than 2 tires. The brakes on all 4 trucks will be the same.