I have an overload story for you. Back when I lived in TX, I was briefly "allowed" by the state to title and register a Japanese Domestic Market KEI class minitruck for on road driving. If anyone is familiar with these trucks, you'll know that they are almost always 4x4 out of sheer necessity, and are powered by 660cc three cylinder engines planted behind the front seats and are accessed via a panel in the bed.
During this period, I was also remodeling my master bathroom, and had selected marble and travertine stone tiles for the shower walls, floor, and bathroom floor. After doing the math to determine the quantites of each, I proceeded to drive said minitruck to work (50 mile one way commute) to stop at the Costco to buy these materials. I never once gave thought to the weight of the load as we were stacking box after box after box of stone tile in the bed of this tiny little truck.
As we were adding the last of the load to the bed, a customer came up and told me that my tires were flat. I looked down, and sure enough, the tires were compressed down to the rim. I had to air them WAY up to even be able to move. I aired the tires up to something along the lines of 60 psi each (rated at about half that), and eased the little truck onto the road. The truck had all of the accleration of an 80,000 pound fully loaded semi truck.
Once I got to work, I grabbed the weight off of the marble and travertine tile boxes. I ran the numbers and came out to over 2600 pounds of tile in a vehicle rated to carry about 800 - including the passengers.
I did call my neighbor who was nice enough to drive all the way into town and take half the load out of my truck so that we had some chance of getting home without breaking the truck. Still with nearly 1400 pounds in the back, I had to tip-toe carefully home.