Здравствуйте, Sshur, Вы писали:

S>но, возможно, на большой скорости добавится наклон и канавка просто будет по диагонали идти вдоль колеса — а там пофиг вперед она смотрит или назад.

Вот тут целая дискуссия на эту тему: http://sgbikerboy.com/2016/12/26/why-do-motorcycle-front-and-rear-tires-have-opposite-tread-patterns/
Вот этот комент мне кажется наиболее разумным:

That is counter intuitive, the reverse pattern at the front will only push water to the center of the tire, that is not the reason why its there. A good rain tire will have a center line, most performance tire have the reverse tread because when the bike is leaned over, the tread would push the water away to the outside of the lean better, if the tread is not reversed, when leaned over water will be pushed to the inside of the lean or the direction the bike is cornering / leaning into, which is bad as it will cause hydroplaning. When going on a straight line, it is not much of a concern as a bike can practically go on the rear wheel alone.