This is sometimes a problem due to the precision fit of the parts. Vinyl is a thermal product which means the warmer it is the more pliable it becomes. If you have difficulty getting your rims to fit the tires, place the tires in very hot water for about one minute. BE SURE TO HAVE ADULT SUPERVISION! Carefully remove the tire using a utensil such as tweezers, and while still warm, press it onto the wheel.