Let the air out of the tube, then take one side of the tire off of the rim and make sure the tube isn't caught anywhere or wrinkled up on itself. Then put the tire back on the rim, allign the valve in the rim hole and put a small ampunt of air in the tube to keep it from getting caught between the tire and rim. You should be able to see the rim tape on either side of the tire. This is an indicator the tube is properly located inside the tire. Then make sure you squeeze the beaded area of the tire together and push it downward into the "well" ( center ) of the rim. This centers the tire/tube on the rim so it seats correctly. Then add about 50% of the required ampunt of air, watching to make sure the tube doesn't escape the tire carcass. Check all around the rim for consistancy of fit. Then continue to inflate the tire pressure to the required amount. You can move the tube inside the tire during the initial mounting process more easily by using talcom powder on the tube before inserting it in the tire.