So no matter how I keep looking at it a set of 15x7 steel rims and mud tires to fit them are still cheaper than similar 16" rims and tires.  However I'm trying to figure out what backspacing I need.  The stock 16x7 aluminum rims have 4" of backspacing and the wheel spokes angle out, away from the mounting surface to clear the calipers.  What I'm wondering is if a 15x7 steel wheel with say, 3.5" of backspacing would clear?  The rim and tire would effectively be spaced out half an inch from the mounting surface this way.  Would half an inch be enough?

I can find 15" rims for $40 locally, but can get custom backspacing ones for around $65 delivered...however I'd hate to do that and still have to buy wheel spacers to make them fit.

Then there's the alternate route of regular 15x7 rims with 4" backspacing and wheel spacers...but I've never felt to hot about those as a whole.

While the backspacing will help, I think it really just depends on the specific wheel style.  For example my stock Tracker wheels are 15x6 with standard backspacing (don't remember what it is) but they are made with a large opening to fit around the brake calipers.  When I seriously plan on getting new wheels  I plan on measuring the interior diameter of my wheels (at the mounting surface) and my brakes, then I whenever I am looking at wheels I will ask the seller what the interior diameter is, so I should be able to figure out whether or not they will clear.  If I am buying new wheels I certainly don't want to have to use spacers tool

i have 15"  on my Grand Vitra put it this way what do u use the truck mainly for ??

I'm getting 16" steel wheels soon.  15's just won't fit without having very little backspacing.  The calipers are too big.