The tires that were OEM on my 2012 2500HD. I now have a 2015 3500HD Dually flatbed with the same size tires. It has always been common practice to use smaller tube to keep tubes from folding. Back when I still ran trucks with tube required tires, probably half the flats were from folded tubes. I was able to salvage my old flaps. But a flap can be made from an old tube. Just anything to keep the tube from rubbing on the wheel.