Poly(ethyleneterephthalate) tire-cord, their preparation method and tire comprising the same

The present invention relates to a PET tire cord, of which a shrinkage behavior index (SBI) defined by the following Calculation Formula 1 is 0.1 (g/d)/% or more under the conditions of the load of 0.0565 g/d and the temperature of 180°C: Shrinkage behavior index SBI = Shrinkage force g / d / Shrinkage rate % , to a method of preparing the same and to a pneumatic tire including the same.