The directional designs are meant to move the water from the center to the outside edges of the tire while moving forward. They dont care if you are accelerating or braking. If it is dry they make no difference, they don't have better traction because of their directional tread design unless there is enough water on the road that they can dispel it better than a non directioal treaded tire. Think of it this way, a slick has zero tread sipes(maximum rubber on the ground) so (all else being equal like compound) they will have more traction, but in the rain they are horrible because they can'tmove water out to the sides, they just push it forward and eventually hydroplane on it.
If I remeber correctly, unidirectional tires have better traction on dry pavement also, because the groves for channeling water away are facing twoards the direction the water is. They need to have less space in the sipes, and can be placed closer together.
At least I belive that was part of the reasoning behind unidirectional tires.
I thought radials were only supposed to be rotated front to back?
Nah it's more of an X pattern. LF to RR, RF to LR.
Or RR to RF, LF to LR.
or LF to LR, LR to RF, Rf to RR, RR to LF.
It all depends on the tires and the person. One is supposed to be the best but I can't remeber. Because every corner wears different.