To provide a core type tire assembly in which the occurrence of a flat tire can be immediately warned to a driver, and a remaining travelable distance is displayed correctly.

A tire internal pressure warning device comprises a tire assembly 3 having a support ring 2, a transmission means 4 which transmits radio a wave signal in a normal condition, and is held by a tread 12 and the support ring 2 and broken to stop transmission when internal pressure is dropped, a reception/warning means 6 which receives the radio wave signal from the transmission means 4 and transmits the warning signal as an internal pressure dropped state when the reception is stopped, a controller 7 to calculate the remaining travelable distance L2 in the internal pressure dropped state based on the warning signal, and a distance display meter 8 to display the remaining travelable distance L2. The transmission means 4 receives the electromagnetic wave from a power supply means 9 as power supply energy.