What size spare not stock wheel will fit underneath truck
 

2011 2.3L 4cyl - Came with 15's from the factory originally. I purchased it with 225/60/16's. Has a full size 15" spare tire underneath the bed. My question is if I were to go up a size to 17's is there room underneath there to attach a wheel and tire that size or is there only enough room for the factory size wheel and tire?
Thanks again for everyone's help.

It is basically the diameter of the tire that dictates how large you can go with the spare tire. The size of the wheel should have little effect. I have a 11.5 x 32" tire as a spare. It does not fit all the way up in there but it has never hit anything while doing some pretty extensive off-road travels. I had a 31" spare tire for many years and it fit snugly all the way in there. I don't know if a 2011 Ranger has the same spare tire space as an 02, I am guessing it does.