Looking for Answers about Kenda K500 Super Turf Tire, 18 x 850-8?

I use two big flat blade screwdrivers or tire irons to wrestle the tire onto the rim, being careful not to ruin the sealing surfaces. Hint: If you get one side of the lip over the rim, push it down to the skinny middle part of the wheel to make it easier to pry the rest over the rim. To get the bead to seat, I put band clamps around the tire at the outer edges, then tighten them up. That gets the beads up close to the rim so it seals enough to hold air. I put air in until the bead pops into place, remove the clamps, and away you go.

8" is the rim size. 8.5" is the tire width. 20" is the nominal tire diameter.

Yes it is the same size. They just don't print the decimal on some tires. Note, though, that some Kenda tires are slightly smaller diameter than spec. My 16x6.50-8 was really just 14 3/4" in diameter. No big deal, just FYI.