  Consider the free orthogonal quantum groups $O_N^+(F)$ and free unitary
quantum groups $U_N^+(F)$ with $N \geq 3$. In the case $F = {\rm id}_N$ it was
proved both by Isono and Fima-Vergnioux that the associated finite von Neumann
algebra $L_\infty(O_N^+)$ is strongly solid. Moreover, Isono obtains strong
solidity also for $L_\infty(U_N^+)$ . In this paper we prove for general $F \in
GL_N(\mathbb{C})$ that the von Neumann algebras $L_\infty(O_N^+(F))$ and
$L_\infty(U_N^+(F))$ are strongly solid. A crucial part in our proof is the
study of coarse properties of gradient bimodules associated with Dirichlet
forms on these algebras and constructions of derivations due to
Cipriani--Sauvageot.
