Tires: truck loan capacities, gross axle weight, tire placard

Question
Barry, we have a 2000 F350 with standard 16" tires.  We carry a 4100# (wet) 2007 Lance Camper and pull a 3 horse trailer with a 1950# tongue weight.  the GAWR on the truck panel is 6820 rear, the tires are rated at 3400.  After 2 rear blow-outs we realized we are probably way over both tire capacity and truck capacity.  We've been looking at the 19.5" Michelin's with a rating of 5500#'s.  Can you explain all this and tell us if the new tires would be a good answer or is our best option to buy a dually?  This may seem like a stupid question, but does the GAWR include the weight of the back of the truck (which is 3320 by itself or 9820 with the camper & trailer)? Does the manufacturer tire capacity include the weight of the truck or is that the capacity of the load not counting the truck?

Answer
NJK,

Your first step ought to be to call Ford and find ought what the load capacity and the towing capacity is for your truck.  Be sure to explain that you are both carrying a camper and towing a trailer.

The second thing would be to weigh the rig all loaded up with as much stuff as you could ever think of carrying.  You are trying to get to a "worst case".  It would be best if you could measure individual corners of both vehicles (if you can get it down to individual tires - great!), but at the very least, weigh individual axles.

The actual axle weight should not exceed the GAWR (Gross Axle Weight Rating).  This is the maximum allowable weight that the axle was designed to carry.

BTW, tire capacities are also all encompassing.  That is the maximum load as measured in the contact patch.  You should also be aware that a tire's load carrying capacity is affected by the inflation pressure.  Check on your tire placard for the original tire size and the proper pressure for that size.  If the pressure listed is less than the maximum listed on the sidewall of the tire, then the actual load carrying capacity of the tire will be less than what is listed on the sidewall.

So here's what I see so far:

The rear GAWR is 6820#, but the tire max is 3400# - If this is a single rear wheel (SRW) then the GAWR is larger than the tire's max by 20# - and that doesn't make sense.

If the truck is a dually (DRW), then this might make some sense.

I'm not clear on this, but did you say the rear axle weighs 9820# with both the camper and the trailer attached?  If so, then you're overloading the rear axle by almost 50% - and that sounds like you need to get a bigger truck.