Lawn tractor tires are low-pressure clones of automobile tires. Because of this, they are not as sturdily made and are, therefore, much more flexible, especially in sidewall construction where all of the action of changing tires takes place. This task will require you to get down on your hands and knees for a short while when removing the wheel from the lawn tractor. If you are not capable of this or don't feel comfortable in this position, you will either need to have someone help you, or you'll have to call in a professional to get the job done.
Put your gloves on to protect your hands.
Place a wooden block, roughly the same width as your tire, underneath the axle for support.
Drain the air from the tire using a flat bladed screwdriver to press on the air valve inside of the inlet stem. If the tire is already flat, go to the next step.
Remove the cotter pin holding the tire on to the axle by bending the ends up with your pliers and then pulling it out. Once the cotter pin has been removed, pull the tire off of the axle. The wooden block underneath the axle will support the front end for later installation of the new tire.
Press on the sidewalls to break the bead between tire and rim.
Insert one screwdriver underneath the front sidewall and pull it up and out over the rim. This first screwdriver will remain here.
Insert a second screwdriver next to the one already in place. Begin sliding it along while prying the sidewall up and over the rim edge. Move slowly and carefully around the rim, and when you are about half way around, the tire will pop free.
Insert a screwdriver under the rear sidewall exactly as you did on the front one, then insert the other screwdriver next to it. Using the same technique, move slowly and carefully around the rear sidewall until it too pops off. The old rubber will now be in your hands.
Place your new tire over the rim and firmly press on the rear sidewall. Move around the entire rim, pressing constantly, and at about the halfway point, the rear sidewall will pop onto the rim. Do the same thing to the front sidewall until it too pops onto the rim.
Pour, or using your fingers, spread some soapy water solution liberally onto the inner rim where the sidewall will make contact, Doing this will make a secure and airtight bead between rubber and rim.
Stand the tire up and begin to inflate it with a hand pump, or preferably an air compressor, to the point where the sidewalls contact the rim, and the tire is holding air.
Put the tire onto the axle of the tractor, push back in the cotter pin and, using a pliers, spread the ends of the pin around the axle to keep the tire in place.
Inflate the tire to manufacturers specifications using a tire gauge and pull out the wooden block.