I've done a lot of reading on this thread but I'm still confused. I have the 2015 XLT Sport SCREW FX4 with 275/65/18 tires. This setup is fine for most driving but I'd like have a second set of wheels and tires for snow, mud and sand. I have the opportunity to buy another set of the same 18" wheels my Sport came with on which I can mount snow/sand tires. But, is a different sized wheel better to mount some off road tires, or is the stock 18" size good enough?

 

The 18's should be fine.

My Lariat comes with 18's but when they came out they were considerably more expensive than 17's so I picked up some factory 17's and use those to run my 10 ply's on for my woods work. I also have 17's for my studs in the winter. When I trade the truck in for the next one, I bolt the 18's back on and trade it.

 

Sounds like buying a used set of my stock wheels and putting off-road tires on them will work well then.