That is the question; the wheel offset, width, diameter, etc determine what size tire will work for any specific application. And for that matter, even the brand and model of tire matters - there is a huge variance for the same size between brands and models. There is no way of knowing if a particular size tire will fit without knowing all of the data. And even then it depends on each particular car's nuances for fender shape/position, suspension settings, ride height, etc, relative to other identical models (no two X's are exactly the same). Naturally this is all assuming that you are looking to achieve the ultimate "fit" with basically zero clearances. But discussing wheel specs, suspension settings, tire sizes, and all the other data is only a start, trial and error may ultimately be needed. I have one of those tire fitting gauges that is adjustable to mimic any size tire and can be fitted to the car to test for clearance. But I've found even that isn't completely accurate - there are just too many other variables involved. So you really won't know for sure until you try. It's all part of the fun of customizing.