Most riding mowers now use a clip with a square key to secure the rear tire to the axle. Early models of MTD riding mowers use only a bolt that threads into the axle shaft. The rear tire can become stuck on the axle shaft when you remove the bolt to change the tire. The meeting point between the rim and axle can seize due to dirt and rust. There is no simple way to remove the tire and rim. The area of contact requires penetrating oil to work through the rust that is adhering the tire and rim to the axle shaft.
Park the MTD riding mower on a solid level surface such as the driveway or garage. Place a floor jack under the rear frame of the mower, and place wood blocks in front of the front tires. Raise the rear of the mower with the floor jack until the rear tires are 6 inches off the ground.
Position a jack stand under the rear frame on each side of the floor jack. Adjust the jack stand arms to meet the frame. Slowly lower the mower to allow the jack stands to support the weight of the mower. Leave the floor jack under the rear frame as additional support.
Spray the mounting bolt with a spray penetrating lubricant. Spray the area behind the tire and rim where the axle inserts into the rim with the spray penetrating lubricant. Allow the lubricant to work for 20 minutes.
Remove the bolt in the center of the rim that secures the rim to the axle with a socket wrench. Models of MTD mowers made in 1986 and earlier do not use a square key or a cotter pin. Grab the tire on each side with your hands, and rock the tire off the axle.
Place the end of a small 1-foot long board between the center of the rim and the outside edge of the rim, if the tire and rim will not budge. Tap the other end of the board with a rubber mallet to move one side of the rim. Move the board to the other side of the rim and tap it with a mallet. This usually loosens the rim enough to pull it off the axle. If necessary, spray more spray lubricant between the axle and the rim, and allow the lubricant to soak.