Liquid drops slide more slowly over soft, deformable substrates than over
rigid solids. This phenomenon can be attributed to the viscoelastic dissipation
induced by the moving wetting ridge, which inhibits a rapid motion, and is
called "viscoelastic braking". Experiments on soft dynamical wetting have thus
far been modelled using linear theory, assuming small deformations, which
captures the essential scaling laws. Quantitatively, however, some important
disparities have suggested the importance of large deformations induced by the
sliding drops. Here we compute the dissipation occurring below a contact line
moving at constant velocity over a viscoelastic substrate, for the first time
explicitly accounting for large deformations. It is found that linear theory
becomes inaccurate especially for thin layers, and we discuss our findings in
the light of recent experiments.