Not much accomplished today with family over for xmas and all that goes with that. I decided that since I had only attached two of the four wheels, I might as well test the other two and see what my total scope (problem) looks like. Well, here is the recap: Wheel #1 - 0 broken lug nuts, wheel #2 - 1 broken lug nuts as discussed in original post, wheel #3 - 3 broken lug nuts, wheel #4 - 5 broken lug nuts. So since yesterday i have gone from 1 broken (sheared) lug nut to a total of 9. Thing are not looking good. Oh, I also busted a twelve point socket that I was using on the key socket for the lug nuts. I guess the breaker bar/pipe combo was too much for it too.
First pic shows broken nut next to one that is not broken. 3rd pic show the first one that i already tried to drill out unsuccessfully (hard to see in pic, but two holes in the broken nut, opposite sides of bolt). You can also see the small test hole in the end of the bolt that i test drilled to confirm feasibility of drilling. 4th pic is the last wheel with 5 broken nuts (groan). And the last pic is just my collection of broken nuts.
As you can see, when the nut breaks, the outside portion screws off and reveals some of the threads. None of them were cross threaded. On the 15 that did come off in one piece, they were also very tight, but once they came loose they screwed off easily by hand. I think my problem is some combination of over torquing and a weak design.
Almost forgot...I tested the second two wheels with my torque wrench at 250 ft-lbs (maximum value for my wrench) and none of the nuts would turn to loosen. IOW, they required MUCH greater than 250 fl-lbs to remove (breaker bar and section of pipe and still had to get on it).