I'm really wanting to widen my GV. I've contemplated wheel spacers etc but not sure if I want to go that route. Right now I'm thinking hard about ordering some steel wheels from RRO (http://www.rocky-road.com/wheels.html) with 2.5 inch back spacing. Now I'm trying to figure out if I should get the 16 inch or try to find a way to get the 15's to fit. Has anyone ever mounted a set of these 15's with 2.5 inch back spacing on a Grand Vitara? If the would fit they'd be the perfect wheel for us. I found a review on some 15's from RRO with 2 inch backspacing and they had some good pictures... anyone think they might fit?   http://www.off-road.com/suzuki/reviews/rrwheels.htm

Hard to tell for sure, but the likelyhood is they will hit the calipers.  I've never heard of anyone getting 15" on a GV.

JDMCRX runs 15's with 3.5 inch backspacing and 1 inch wheel spacers (effective backspacing of 2.5 inches). I believe he may have also ground down the caliper... I comes down to the inner diameter of the wheel where the brakes would be which is different on every wheel. I just thought that with a small 2.5 inch backspacing that the caliper might be clear of the that inner part of the wheel that typically has the smallest diameter (if you know what I'm saying)

I may be wrong about this, but it seems to me that a backspaced wheel is not the same as the equivalent spacer.  It puts the tire in the same place, but the spacer will also position the hub of the wheel outwards.  My understanding is that it's the material close to where the hub joins the rim which contacts the caliper.