The smooth tyre means that the rubber can contact the ground in the largest area, which will bring the best grip in a flat and dry track environment. However, once encountering water or sand, the bare tyre that cannot adapt to the sand and gravel pavement will become very dangerous due to its lack of drainage capacity. The appearance of water and sand on the street/mountain road is unpredictable and unavoidable, so the bald tyre cannot be used on the road legally and can only be used as the track tyre.
The deeper and more patterns of motorcycle tyres, the better the tyre's drainage capacity and its ability to deal with uneven roads such as sand and gravel, but also means that the grip is reduced (the area of rubber in contact with the ground is reduced). However, this relationship is not completely positive. Nowadays, many tyres with deep tread patterns (sports touring cars, and some tyres for adventure vehicles, such as Pirelli Angel tyres) have deep tread patterns, but the grip is still quite good. Experienced racers can use these tyres on the track to grind their knees and turn corners.
The trend of motorcycle tyre pattern has a certain impact on the sensitivity and bending ability of the vehicle. Generally speaking, the longitudinal pattern is helpful to improve the passing ability in sharp turns and high-speed turns; The transverse pattern can improve the stability of vehicle braking.