http://www.tobysexton.com/home.htm , those rims hold recapped aircraft tires , the rubber flap , protectes the tube , the tires are between 28 and 32 plys , even on the side walls , they are recapable if you don't run them into the threads ------------they are very good tires that will very seldom get a flat and if they do you usually don't even know it unless you pick up some weight ------------look closely on the side and you should see " good to 210 knots " , if I remember right the ones used on a 7 series were A-10 Warthog tires and the 8 series were F14 or 18 -------what is really nice about those tires , if you are running tracks on top of them you will very seldom get a flat but if you do it is possible to easily repair the flat without removing the tracks