Getting a small tire back on a rim can be a frustrating exercise. Experienced tire changes all have their own tips and techniques, but their advice often includes the idea of first deflating the tire and removing the tire's edge (or bead) from the rim. Many people suggest using a rolling motion with the palms of your hands for the best results, but others use a "two-thumb" maneuver to get the job done.
Deflate the tire first and remove the valve-stem-core using a small valve-stem-core wrench tool first. If you don't have this specific wrench, you could use a rubber or plastic hammer, operating it carefully to avoid destroying the rim if you accidently connect with it.
Push the bead (the edge) of the tire loose from the rim all the way around, on both sides. It works much better if you start removing the tire at the valve stem. Insert the tire lever or tire iron and carefully pry the tire over the rim. Once you have taken the inner tube out of the tire-casing or rim, repair it or replace it.
Put the inner tube back into the tire. Put one side on at a time. The first side goes on quite easily, without a struggle, but the second is much harder. Don't forget to insert the valve stem at this stage, and then starting at the valve stem, work the second edge (bead) around. You need some slack to accomplish this, and you achieve it by making sure the first bead is loose in the center of the rim. There are different techniques, but the most commonly touted is to roll the tire onto the rim using the palm of one's hands, almost in a kneading motion.
Inflate the tire. The stem should be straight when the tire is inflated. Ensure that the tire is centered properly by checking around the rim area.
