  Let $G$ be a $3$-connected graph with a $3$-connected (or sufficiently small)
simple minor $H$. We establish that $G$ has a forest $F$ with at least
$\left\lceil(|G|-|H|+1)/2\right\rceil$ edges such that $G/e$ is $3$-connected
with an $H$-minor for each $e\in E(F)$. Moreover, we may pick $F$ with
$|G|-|H|$ edges provided $G$ is triangle-free. These results are sharp. Our
result generalizes a previous one by Ando et. al., which establishes that a
$3$-connected graph $G$ has at least $\left\lceil|G|/2\right\rceil$
contractible edges. As another consequence, each triangle-free $3$-connected
graph has an spanning tree of contractible edges. Our results follow from a
more general theorem on graph minors, a splitter theorem, which is also
established here.
