spacers don't have an offset
to do it right, you would want to get wheels with a different offset from stock, and forget about the spacers. next best, would be to get longer wheel studs and spacers. almost as good, would be to run minimal spacers with existing wheel studs. (which i wouldn't do) worst idea would be to get thick spacers that bolt to the hub, and then the wheel bolts to the spacer. (strictly, only, specifically for show and off road use ONLY - a danger to everyone, not just you)
if you think you REALLY need spacers, to find out how much spacer you can run, measure from the outside edge of the tire to the inside edge of your fender and thats the maximum spacer thickness you can get with our rubbing.
