I have a 13 SHO PP and have been wanting to get a spare tire in lieu of the air compressor provided. I stopped at a local junk yard and picked up a 17 inch spare tire and jack kit. Unfortunately the 17 inch spare tire was to small. Looks like 18 inch must be the minimum. Don't know if anyone else has tried this and could offer any suggestions on where you got the spare tire and size???? I'm having difficultly finding a spare tire locally as I am trying to avoid shipping costs.