Biliebob, as a mechanical engineer working in the auto and transportation industry, I have to say CampStewart made some very logical points. I often like your posts, but today tou seem to be the one looking for an argument... Posts can disagree without being argumentative.
To another point above, most dually trucks have a ~6" spacer bolted onto the front axle. I'd venture that almost nobody ever checks the nuts that bolt the spacer on. I've never heard of one coming off. That's a pretty good indication that when properly installed, spacers don't just "rattle loose".
Nor do wheels.
Correctly installed and torqued lug nuts will NEVER rattle loose. I submit to you that a wheel that "rattled loose" was actually installed incorrectly in some way. I have seen broken studs because people didn't remove the brake retaining clips when installing wheels with a flat face, or because someone "tightened" with lugs with a battery powered impact and they worked loose due to lack of torque, or because they didn't tighten them at all. But a cone seat lug nut will NOT "rattle" loose when properly torqued. Ever. I submit that anything that can "rattle" was not torqued properly in the first place.
Wheel bearing issues aside, I have also used wheel spacers to widen a rear axle that was a bit narrow with NO ISSUES, including really heavy occasional loading. (3/4 ton truck). Because of bearing issues, I would NOT run excessively wide spacers on anything, but I'm comfortable with 1.25-1.5" spacers where needed.
As a final thought, if you run significantly taller tires on OE wheels, spacers actually can be used to correct the scrub radius, which goes more negative as the tires get taller.
