Repairing a leak in a lawn mower tire is not much different than repairing one in a car tire. If the leaking tire is in good shape and the leak is from a small puncture hole, then using a tire patch kit should save you the cost of having to buy a new tire. However, if the leaking tire is old or has somehow gotten ripped, then you will need to purchase a new one.
Put the lawn mower into neutral and push it onto a hard, flat surface. Do not ride it if the tire is flat, you could easily lose control.
Engage the lawn mower parking brake and remove the keys from the ignition.
Place wooden blocks both behind and in front of at least two of the tires to help prevent the mower from rolling.
Loosen all the bolts on the tire using a wrench. Do not remove the tire.
Check your maintenance manual to find out where the best place is to lift your specific lawn mower with a jack. Place the jack in the designated spot and lift the mower just enough to be able to get the wheel on and off easily.
Finish unscrewing the tire bolts and slide the wheel off the axle. You can use a garden hose to wash off any dirt that has gotten stuck on your mower behind the wheel.
Mix a bit of dish soap and water in a squirt bottle. Squirt this on the leaking tire. Escaping air will cause the soap/water mix to bubble and you will find your leak.
Purchase a tire repair kit from the hardware store. Follow the manufacturer's directions to repair the leak.
Use an air pump to refill the tire. The recommended PSI will be on the side wall of the tire. Use a pressure gauge to make sure you fill it to the correct amount.
Slide the tire back on the axle and firmly tighten all bolts. Lower the jack until the mower has all four tires resting on the ground.