A tire/wheel assembly comprising a wheel having a rim, a pneumatic tire mounted on the rim of the wheel and a noise reduction interior member disposed in the cavity of the pneumatic tire. The noise reduction interior member includes left and right elastic rings fitted to the rim and an annular body attached between the elastic rings. The annular body is configured such that an annular cavity portion surrounded by the noise reduction interior member and the pneumatic tire has a cross-sectional area that varies in a circumferential direction of the tire.