Dear Tom and Ray:
My roommate and I have been arguing about tire traction. I said that a racing slick (or just a bald tire) has more traction in a dry environment, and is able to stop a vehicle faster on a dry road. He said that a tire with tread has more traction and is able to stop a vehicle faster. We are on the verge of war: I've taken his dipstick hostage, and he's got my hubcaps. Please help end this war and bring peace (and my hubcaps) back to this house. -- Matt
RAY: He needs to return your hubcaps with a humble apology, Matt. You're right.
TOM: On a dry road, a racing slick will give you more traction. Why? Because there's more rubber surface area actually in contact with the road. That's why drag racers, who need as much traction as they can get, as quickly as possible, use "slicks," or tires with no tread.
RAY: But remember, as soon as a half-ounce of rain comes out of the sky, you'll be in the ditch with your slicks. The problem with slicks is that when there's water on the road, the tire rolls up on top of it, and the water has nowhere to go. And when the tire's on top of the water, NONE of its rubber is touching the ground! That's called hydroplaning, and it severely limits your ability to turn or stop.
TOM: The purpose of the grooves in treaded tires is to provide pathways for the water to escape. That way, while the rest of the rubber is maintaining full contact with the road, the grooves are channeling the water out back, behind the tire. And onto the windshield of the poor schnook driving behind you!