  We establish a universal consistent Kaluza-Klein truncation of M-theory based
on seven-dimensional tri-Sasakian structure. The four-dimensional truncated
theory is an N=4 gauged supergravity with three vector multiplets and a
non-abelian gauge group, containing the compact factor SO(3). Consistency
follows from the fact that our truncation takes exactly the same form as a
left-invariant reduction on a specific coset manifold, and we show that the
same holds for the various universal consistent truncations recently put
forward in the literature. We describe how the global symmetry group SL(2,R) x
SO(6,3) is embedded in the symmetry group E7(7) of maximally supersymmetric
reductions, and make the connection with the approach of Exceptional
Generalized Geometry. Vacuum AdS4 solutions spontaneously break the amount of
supersymmetry from N=4 to N=3,1 or 0, and the spectrum contains massive modes.
We find a subtruncation to minimal N=3 gauged supergravity as well as an N=1
subtruncation to the SO(3)-invariant sector. We also show that a reduction on
the homogeneous space N^{010} enhances the universal tri-Sasakian truncation
with a Betti vector multiplet.
