  We consider the Cavalcanti-Foster-Fuwa-Wiseman inequality~\cite{achsh} which
is a necessary and sufficient steerability condition for two-qubit states with
two measurement settings on each side. We derive the criterion which an
arbitrary two-qubit state must satisfy in order to violate this inequality, and
obtain its maximum attainable violation in quantum mechanics. The derived
condition on the state parameters enables us to establish a tight monogamy
relation for two-qubit steering.
