Reduced tire friction on merely damp roads?
 

I momentarily posted this to the Tire Pressure/Handling string. I then
realized it was off topic there. It deserves its own consideration. :thumbup:

"Rubber friction on wet rough substrates at low velocities is typically 20%–
30% smaller than for the corresponding dry surfaces. We show that this
cannot be due to hydrodynamics and propose an explanation based
on a sealing effect exerted by rubber on substrate “pools” filled with water.
Water effectively smoothens the substrate, reducing the major friction
contribution due to induced viscoelastic deformations of the rubber by
surface asperities. The theory is illustrated with applications related to
tire-road friction."

This surely goes hand-in-hand with the idea that when it first begins to rain,
oil on the roadway floats to the top and causes slipperiness.

Hear Ye! Hear Ye! Read All About It!

That's pretty cool! Good to know.