Hmmm. No "this thread is useless without pictures" smiley. Oh, well, let's shed some light on the matter! Here's the spare on my I4 XLE:
Eye-balling it with a tape measure, the spare doesn't appear to be
quite as big in diameter as the "real" tire/wheel combination. Check out that "terraced" well, though -- maybe there's enough height in there for a full-size tire/wheel.
Here's the cover directly atop the spare, which holds a few jack tools underneath it:
Hmm, what's that yellow sticker say? Well, this:
1 inch reduced ground clearance? Yeah, that's about the difference between the two diameters -- this thing
is a little smaller than "full size."
So, would a "full size" tire fit into that well? Man, I don't think so!! It would be a
VERY tight fit if it did!
But.... Isn't this a whole lot better than the usual tiny little "donut" spare? I sure think so!
I've got more pictures, and some close-ups of that tire, but I'm late on my lunch hour, so I've got to run for now! Hope this helps!