I have 17x9 cobras and got a flat the other day. Had to put on the stock spare which was pathetic, and to make things worse the tire shop had to order me a new tire which took three days to get so I was driving around with that lame spare on. I was thinking the same thing, maybe get a fifth cobra wheel, and have a full size spare. I didn't try when I had the wheel off but it doesn't look like it would fit, best thing to do would be take out a measuring tape and take some measurements. Definetely a good idea though, especially after having to experience the stock spare tire or of course if you dont have a spare at all. I was wondering if anyone has a full size wheel as their spare and if it fits in the original spot.