They're 275x40x17 on 17x9-1/2, -15.78mm offset on the front, 315x35x17 on 17x12, -41.18mm offset on the back. I was going for the deep dish look on the back, I think I pulled it off. I got too aggressive on the back offset and had to put 1/4" spacers on. I've also got travel stops on the back.
This sizing worked for me but I have the GNX flares that give me more space to work with and I have a rock hard suspension. These probably won’t work on a GN with soft (stock) suspension. You need to take some measurements and see what size tire you can fit in. Make all your measurements from the mounting flange surface. The tires shouldn’t come inboard anymore than 4½”. If your suspension is soft or lowered make sure the tires will clear the fenders.
Once you know the size of tire you’re going to use selected the rim width you need. All tires sizes will have a range of rim sizes that they can be used with. The measure rim width will keep the sidewalls relatively square. Keep in mind that the section width listed for a tire will change by about .2” for every .5” of difference from the measure rim width. Last select the offset you need. This will move the tire centerline away from the mounting flange surface. A negative offset will move the tire outboard.
As you can see I’ve got the fronts tucked in. The back is lifted (with air bags) enough to prevent contact. If you need any help post your measurements.
or put some 26's on it
