Xowner is correct. Your tire size is 18.5 X 8 - 10. 18.5" tall tire x 8" wide (tread) on a 10" diameter wheel. Your wheel can be either 10X8 or 10X9 - either will work. 10" diameter X 8" or 9" wide. Peepers - when confused - just think about your truck tires 31 X 10.50 - 15 - I know you know what that means.
I have my ice tires mounted on micro sprint 10X10 wheels, and my 18 X 11 - 10 Fast trekkers barely fit. It makes them even lower profile and wider. I don;t think ATV wheels come in 10 X 10 - but I could be wrong.
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