Factory wheels have 6.25" of back spacing and that allows them to sit centered over the bearings. Among other things, this gives you optimal steering axis inclination, better scrub radius and will help keep things like your ball joints and wheel bearings from wearing out prematurely. Now, the problem with this is that when you install bigger tires, wider tires and or with suspension components that'll sit closer to your tires, you WILL have rubbing issues at a full turn and or at a full flex. Wheels with less back spacing will push your tires outward and that will help make it possible to run them and without rubbing issues. The down side to that, is the fact that your tires will stick further out and that will cause you to have a steering axis inclination that is off, reduced scrub radius and a wheel that is no longer centered over the bearings and that will cause them and your ball joints to wear out prematurely. Not like, tomorrow but sooner than they should. Needless to say, the more back spacing you have or the closer you can get it to factory, the more benefits you will see in the areas just mentioned. However, your choices are limited and if you go too much, you will still have rubbing issues - as did I and ended up having to run wheel spacers. 3.5" is the most common wheel back spacing you can find and it will help to clear big wide tires with ease and that's why most people run them. Hope that helps.