I have a John Deere 717A with the pnematic front caster tires and am looking for a replacement (run flats), like on the new 800 series Z-traks. I dont want to spend a lot, just figure it will cost me less in the long run if I invest in better tires now before these wear out. Wish they came standard back then. Any suggestions other than the dealer? Who sells these cheap and can they be put on the same rim or do they come with their own? Any suggestions would help.