I'm using a 15" Goodyear collapsible off an old LIncoln, mounted on a narrowed (5.0") PSE aluminum wheel.
Have only had one flat in 15 years on the road with this car, and have not had to use this collapsible - the sidewalls of my old Goodyear Gatorbacks were so stiff, I was able to limp to a gas station and air the tire back up and get home safely.
Jeff