Having a full size spare is just smart planning. If your tire goes down on the trail you still have to navigate your way off the trail crawling over rocks and such. I could limp it off with my stock spare but it would be easier and safer I think to have a matching spare with me. Also the ability to carry a full size spare means I can leave my stock one in place and have two spares now for the trails. The stock one of course being the emergency spare to the spare.