Most riding mower owners know that a flat tire should be changed. However, even slightly deflated tires need changing just as urgently. A low tire will cause your Murray riding lawn mower to mow your grass unevenly and put undue stress on its frame. And, according to reports to Consumer Affairs, many Murray riding lawn mowers have a problem with tires that won't retain air very well. If you change your tire but still find that it has trouble maintaining air pressure, it may be time to contact the manufacturer.
Park the mower on a level, concrete surface.
Raise the tire. Place a jack near the tire that you want to change. Then crank the jack so that it lifts the tire a few inches off the ground.
Let the air out of the tire. Remove the valve stem's cap. Then use your flat-head screwdriver to press against the side of the valve until all the air escapes.
Remove the tire. Pull off the hubcap off with your hand. Then pull out the cotter pin with your hand (or with a pair of needle-nose pliers if it is stubborn). Slide off the washers.
Pull the tire and rim off the axle. Lay the rim on the ground with the outside facing up.
Break the bead of the tire on both sides. The bead of the tire is the inside edge of the tire that makes contact with the rim. Wedge a flat-head screwdriver between the lip of the rim and the bead and press down until the bead detaches from the rim. Continue around the circumference of the bead until it is no longer stuck to the rim.
Separate the tire and the rim. Start with the top bead and pull it over the lip of the rim. The easiest way to do this is to use the flat-head screwdriver to pry it over the lip section by section. Then pull the bottom bead up to the top lip of the rim and pull it over the rim (this side of the bead can easily be removed by hand).
Put the new tire on the rim. Coat the bottom and top bead of the new tire with tire lube. Force the bottom bead of the tire over the top lip of the rim (again, the flat-head screwdriver may be helpful here), followed by the bottom bead.
Secure the ratchet strap tightly around the tread of the tire. This will flatten the new tire out so that it makes firm contact with the edge of the rim.
Reattach the tire and rim to the riding mower. Slide the tire on, replace the washers and then the hubcap.
Fill the tires to roughly 7 psi. Then remove the ratchet strap and continue to fill them to 14 psi.
Lower the riding mower and remove the jack.