Sealing is at the Origin of Rubber Slipping on Wet Roads
  Loss of braking power and rubber skidding on a wet road is still an open physics problem, since neither the hydrodynamical effects nor the loss of surface adhesion that are sometimes blamed really manage to explain the 20-30% observed loss of low speed tire-road friction. Here we advance a novel mechanism based on sealing of water-filled substrate pools by the rubber. The sealed-in water effectively smoothens the substrate, thus reducing the viscoelastic dissipation in bulk rubber induced by surface asperities, well established as a major friction contribution. Starting with the measured spectrum of asperities one can calculate the water-smoothened spectrum and from that the predicted friction reduction, which is of the right magnitude. The theory is directly supported by fresh tire-asphalt friction data. 
B. N. J. Persson (1), U. Tartaglino (1,2,3), O. Albohr (4) and E.   Tosatti (2,3,5) ((1)IFF, FZ-Juelich, Juelich, Germany, (...