Yeah...Good example amrg. Wheel calculation is a real mess these days. Not only is there the "offset" and "backspace" math...but also the inches & metric conversion. Sometimes hard to stay on top of it. At first you might think a -12mm offset is crazy, and you might wonder why it would be set so far outboard?....then you realize the stock wheels are +38mm (7.5" rim with 5.5" b.s.). Suddenly that number doesn't seem so bad!
I always go back to what I knew from the 70s & 80s, when every truck ran 0-offset wheels. Basically an 8" wide wheel had 4" backspacing. It made the math simple. But nowdays most stock vehicles have the wheels steeply offset to the inboard, and we don't have near the wheel-well area that we used to back then (except for the H3). Long story short...H3 guys typically run a 9" wide wheel, and the -12mm seems to work well for most of us (including Rancho lifted trucks). This offset & width actually comes very close to the old 70s & 80s truck wheels in terms of fit and appearance. I would never run POSITIVE offset wheels but, then again I don't have sub-woofers and tv-screens all over it either. To each his own, I guess.
One final thing: Make sure you get wheels with at least a 4" centerbore (approx. 100mm). The H3 has larger hubs than many other vehicles (including all the other GM 6-lug trucks), so they need a larger hole in the middle to clear them. That trips up a lot of H3 owners, and more than once I've stories of guys ordering wheels only to find out later, that the centerbores are too small.
