What is the name of a bicycle tire with no tread?

A bicycle tire with a smooth surface and no tread pattern is called a slick tire. Slicks are designed to maximize continuous rubber contact with the road, especially on paved surfaces.

Unlike a knobby tire, a slick tire has no raised blocks intended to bite into dirt, gravel, or soft ground. The smooth profile can reduce rolling resistance and is common on road, track, and urban bicycles. Some tires marketed for road use have only tiny grooves or dimples, so they may look nearly slick without being completely pattern-free.

A frequent misconception is that grooves are always needed to prevent a bicycle from sliding on wet pavement. Bicycle tires are narrow, run at relatively high pressures, and have a rounded cross-section; they generally do not aquaplane like wide motor-vehicle tires. On loose surfaces, however, tread can improve control, which is why mountain-bike tires are often knobby.

“Slick tire” describes the tread pattern, not the tire’s construction. A slick can be tubed or tubeless, narrow or wide, and made for racing or everyday road riding.