Tubeless tires on lawn mowers will eventually fail. Although you could take the tire and wheel to a shop to have the tire changed, changing a tubeless lawnmower tire isn't particularly difficult. Tubeless tires are held on a rim by a rubber covered metal band called a bead. The hardest part of changing a tubeless tire is getting the bead over the rim. By using some common tools, the process isn't particularly difficult.
Remove the valve from the tire stem to allow all air to flow out of the tire.
Wrap a ratcheting cargo strap around tread of the tire in the center of the tread. Tighten the strap until the center of the tire is pressed fairly close to the inner rim. This will help remove all air in the tire and will reduce some of the tension on the sidewall beads.
Slip a stout flat blade screwdriver under the bead in one of the side walls. Press down and out on the screwdriver until the bead pops out from the rim.
Slip another screwdriver next to the first. Work this screwdriver around the rim popping the remainder of the sidewall bead off the rim. In some cases, you may need three or four screwdrivers, depending on the tension on the bead and the size of the tire.
Release the cargo strap and remove it. This will make it easier to remove the final bead to release the tire from the rim.
Slip a flat blade screwdriver under the final bead and lift the bead over the lip of the rim.
Slip a second screwdriver next to the first and work the bead off the rim, moving the screwdriver as the bead releases until the tire is free.
Apply dish soap to the bead of the new tire. This will help the bead slip into place.
With your hands, slip one part of the bead onto the rim. Clamp this in place with a pair of vice pliers. Be careful not to damage the bead or rubber by applying too much pressure.
With a screwdriver, work the rest of the bead on to the tire by slipping the screwdriver under the bead and lifting it over the lip of the rim.
Use a screwdriver to lift the second bead over the rim.
Clamp the vice pliers to the rim to keep the first bit of the second bead in place. Use a screwdriver to work the second bead over the lip of the rim.
Rinse the newly installed tire thoroughly to clean off the dish soap. Install the valve and inflate the tire.