An inflatable spare... Wouldn't that be retro! The 70's E-bodies had one avilable -- necessary since the 'Cuda had the smallest trunk in the industry and the Challenger wasn't much bigger! I'm not sure how reliable they were, and I don't think you can get functional inflator bottles anymore, so I carry a full size 14" tire, just in case I lose one of my 15" Goodriches. I figure it's at least enough to limp home on.