Ditto on DeesT's comments. When I was shopping for wheels for my truck (also an XE), I looked at 18" first before deciding on 17's. 305/60-18's will be the correct size height-wise if you are looking at performance street tires. Can't talk to all-terrain tires; sorry. For the 17's I bought, I'm running 275/65-17's which are nearly the same height as the stock tires on the XE. The wheel size I bought is 17x8; the stockers are 17x7.5". Here is the formula for computing tire height: 275 x .65 x 2 divided by 25.4 + 17. Translated, you multiply the first number of the tire size by the aspect ratio (.65 or 65%), multiply that by 2, then divide that by 25.4, and then add to that the size tire (15, 16, etc.) to get the height of the tire. For the 18" tires I mentioned, it would be 305 x .60 x 2 divided by 25.4 + 18. As long as you stay within 10% of the height of the original tire, you should not have to have your speedo recalibrated. OBDII has that variance built into it, if I remember correctly. Also, and I'm not telling you what to do, but if you decide to go up to 20's or larger, you may want to give some thought to upgrading your brakes. The large diameter wheels significantly increase the rolling mass of the tires/wheels, and the stock brakes may not be up to handling the extra load, especially if you hot foot it a lot. I can't speak to the reasoning behind all of this, but I watch the "Trucks" TV show a lot and every time they increase wheel sizes (3 or more inches) on the trucks they build, they always install larger diameter rotors and usually quad-piston calipers. FYI.