[freebeard]

The only connection between the car and the road is the 'contact patch' of the tire (absent a grounding strap, of course). A wider tread helps cornering, a longer patch helps the ride. A softer material helps grip, and thus cornering; a harder material helps lower rolling resistance, and thus helps mpg and hurts stopping distance.

There's a lot to consider. Did I mention hydro-planing?

EDIT: I see there was more than one page. Never mind.