  We compute the canonical integrals associated to wheel graphs, and prove that
they are proportional to odd zeta values. From this we deduce that wheel
classes define explicit non-zero classes in: the locally finite homology of the
general linear group $\GL_n(\ZZ)$ in both odd and even ranks, the homology of
the moduli spaces of tropical curves, and the moduli space of tropical abelian
varieties. We deduce the existence of a doubly infinite family of auxiliary
classes in the even commutative graph complex.
