An adjustable airless tire system with changeable supporting structures optimizes the contradictory relationship between a suspension potential and a tension of a tire according to changes of road conditions. The changeable supporting structures can be selected from one of three separated and compatible parts, including metallic rods, or springs or spring-loaded shock absorbers according to customer's requirements and usage of a vehicle. A metallic cable is used to maximize the suspension potential of the tire and a control component is used to regulate the tension of the tire. A curved tire forms a closed space between the tire and a rim to prevent foreign objects from sticking between them. Therefore, the invention possesses advantages of oil efficiency, affordability, comfortability, controllability and safety.