Most lawn tractors or riding mowers use tubeless tires. These are relatively easy to mount, and the process is bit like mounting a car tire. Once you have taken the old tire off, it is best to mount the tire before reattaching the tire to the axle or spindle. That way, you have more room to maneuver the tire onto the rim, which can take a bit of elbow grease.
Place the lawn tractor rim flat on the pavement.
Generously apply tire lube to the "bead" of the tire or the interior portion of the tire that will come into contact with the rim of the tire.
Position the tire on top of the rim, at a 40-degree angle. Start with the lower portion of the tire. Force the bottom bead over the lip of the rim. Then continue around the tire until the bottom bead is completely below the lip of the rim.
Force the top bead over the lip of the rim. The top will likely be more difficult than the bottom. To help force it over the lip of the rim, wedge the tip of a flat-head screwdriver underneath the lip of the rim and push down on the bead to force it over the lip, section by section.
Secure the ratchet strap around the tire. Tighten it so that the bead of the tire is flush with the lip of the rim.
Fill the tire. Use the air compressor to fill the tire with a little more than half of the manufacturer-dictated psi. Then remove the ratchet strap and fill the tire the rest of the way.