Answer: The small spikes on motorcycle tires (vent spews) are a by-product of tire manufacturing. However, these small spikes have no effect on the tire's operation. In fact, these fibers are properly called vent spews. 

Tire molds are often designed with many small vents so that air bubbles can escape, preventing air bubbles from forming inside the tire. When that happens, both the air bubbles and a part of the melted rubber also escape through these vents. This is considered the result of the formation of vent spews.