I always assumed slick (tread-less) tires were more prone to loss of traction in the wet. That is until I read this answer on the bicycles SE which claims that bicycle tires are too thin, round and firm to experience hydroplaning. Is there any research to back these claims?
Jobst Brandt, author of "The Bicycle Wheel" (which explains how to build strong bike wheels and which includes a finite-element analysis of spoked wheels) lays out the argument at Sheldon Brown's site:
I've ridden both but mostly slicks. I haven't had significant trouble with either on wet tarmac, though I really notice a difference between 25mm and 28mm wide tires on wet mountain descents. The wider tire (and hence larger contact patch) gives much more traction on turns and seems to have a much greater effect than the tire surface pattern.
That said, I doubt many cyclists get fast enough to hydroplane on wet roads. I've done above 45 mph (75 kph) downhill on dry tarmac in good visibility which is more than fast enough to hydroplane a rectangular cross-section tire, but I would never do that in the rain because water hides potholes. Even if that weren't a problem and I had visibility around turns, in the rain you have to pump brakes to keep your rims (which the brake pads grip on almost all road bikes) clear of water which has the side effect of limiting speed.