  We calculate threshold corrections to the running gauge and Yukawa couplings
in the Exceptional Supersymmetric Standard Model (E6SSM) and analyse the more
precise and reliable mass spectra in a constrained model (CE6SSM). Full
expressions for the corrections are provided and the implementation into a
spectrum generator is described. We find a dramatic reduction in the matching
scale dependency of the masses of many states and observe a significant
adjustment of the correlation of low-scale physical masses and high-scale
parameters. Still, in substantial regions of parameter space the mass of the
lightest Higgs is compatible with the new boson discovered at the LHC and the
model satisfies limits from collider searches for squark, gluinos and Z'
bosons. We study the implications for gauge coupling unification from a new
dependency of the spectrum on so-called survival Higgs fields which cannot be
addressed without the inclusion of the threshold corrections.
