  The difference between the Faltings height of an abelian variety $A$ defined
over a number field $k$ and its stable height is measured by the so-called base
change conductor. In this paper, we give a uniform bound of the base change
conductor in terms of the dimension of $A$ and the degree of $k$. This allows
us to reduce the generalized Szpiro conjecture to the semi-stable case.
