A tire comprising a plurality of cavities formed on each of the first and second tire sidewalls. The cavities are extending longitudinally from a cavity opening up to a predetermined distance in the radial middle portion, wherein each cavity comprises a bottom surface and at least one cavity sidewall surface extending from the bottom surface to the cavity opening, said bottom surface and at least one sidewall surface defining an unpressurised cavity space. At least one of the tire cavities comprises at least one structural element extending outwardly from at least one of the cavity surfaces.