I know . . . these were a new set of tires as well . . . roughly 5000 miles on them!
As for the axle, not sure why it went flat, which is why the tires are wearing on the inside edge.
Glen from Dexter looked at it at the Vegas Rally and said possible causes are overloading (which we have not done) or from towing it too high in the front.
It is a little high in the front, but not enough to do this kind of damage, however, he said that we don't know how it was towed to the dealership from the factory!
Here is a shot a couple of hours after we left Vegas (and about 200 miles before we had the tires switched):
Click on images to see the whole thing
I don't think the front is high enough to cause the rear axle to flatten out . . . but what do i know?
I will be taking it to the CAT scales in the next week or so to get each wheel weighed as it may be covered under warranty, but Dexter won't cover it without those numbers.
Here is a shot of the rear axle that I took while it was parked at the Oasis in Vegas:
We stopped to have the rear tires reversed on the wheels so they would wear down the other edge of the tires, but discovered one of them (right rear in this photo) was bulging and starting to separate, so put the spare on that wheel instead.
The inside edges of the rear tires were almost totally bald when they were swapped.