Came across a set of used 18.4-26 diamond tread Goodyear tires. I was told they were 6 ply but more likely 8 ply. Have been on a John Deere combine. Tread looks okay but there is weather checking on sidewalls and tread. Considering getting them for back-ups for a Gleaner C2. Tires currently on the Gleaner are the same size, tread pattern, and brand but in a little better condition so they would match if I only had to replace one. Combine used for grain only and no hillside or steep fields. Considering the price of new tires, if I lost one of those currently on the Gleaner, I would be in a bind. What is your opinion of these tires? How much would they be worth to you? How difficult have you found it to locate better used tires of this size? Appreciate your opinions.