Well, you are in a pickle here. You have exceeded even the design factor for your suspension. I enjoy reading how some posters say there is a design factor of 30% built in. What comedy that is. Do you think Dodge, Ford or Chevy wouldn’t advertise that extra 4,000 lbs of capacity, when the maximum load and towing capacities are such an important marketing tool? While I worked with Ford engineers on their SVT program and had them riding in my race cars and driving their cars, with all these wires going everywhere to monitor. The design standard that was often spoken, is less than 10%.
Personally I would be hesitant in carrying my family and putting others at risk on the road with being more than a ½ ton overweight. Sure, like someone once said; they live in Florida and travel just to and from the beach, so it is not like they are driving in the mountains. But, there are those places where people run stop signs, change lanes and enter roadways unexpected requiring one (in this case a top heavy vehicle) to take corrective action to avoid a potential collision.
Be sure not to concentrate on just the tires. Remember the Wheels the tires are mounted on and check to see if you can put a hotter brake pad on your calipers. But remember, you are going to have increased wear on your unsprung parts, such as bearings and axles, as well as your drive line (transmission/rear gears/driveshaft/Main bearings), as well as your steering components.
Bigger truck or smaller camper.
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