[flybouy]

I think some confusion over axle weights vs payload vs gvwr is in how those components interact. A max axle axle rating is just that, the maximum amount of weight that axle can support without failing.

Let's look at rear axle weights as many folks think that directly sets or should set the payload. That GRAWR number however does not mean that the truck's bed will support that much weight. It also doesn't mean that the frame won't twist or the driveline won't fail, or the transmisdion won't "grenade" if loaded to the GRAWR. It simply means the rear axle and ONLY the rear axle can support that much weight.

At the end of the day those numbers are set by the manufacturer becwuse the government says they have to. How do the manufacturer derive to those numbers? You'll have to contact them to answer that. But there it is, the "do not exceed ..." displayed on every truck. Exceed those numbers and no alarms go off, the police don’t get called, and many folks motor on every day over the payload rating. Many folks also cruise along with no insurance, suspended license, and exceeding the speed limit or impaired. And just like driving without a valid license or insurance no one may ever know unless you are involved in an accident. If that accident results in death or injury you can pretty much bet it will be a subject of discussion.