I looked under my 2013 Ram 1500 and there is the factory spare. Can I put a "real" tire on the rim and will it still fit under the truck bed? What size of tire should I put? Should I put the same tire size as the spare? Is it OK to use the spare tire rim?

 

Are they all 17" spares? The one I seen when searching was a 235/85/17 which is 32.7" tall but 1.6" narrower than stock 20".

I'm sure you can put a normal tire on it without issue since the overall diameter is going to be the same. The only loss you'll have is that it will be lower.

As for putting an aluminum wheel under there....the bore is smaller and the holder wont fit through.

 

At least mine is. You are 100% correct on the tire size. I think that I will go with a 285 70 R 17. It will be a little shorter than the 20"s but not nearly as skinny. It will be a pretty good match for my sand tires.