I'm prepared to hazard a guess. With that bolt, you have to find a way to apply enough torque in the limited space between the axle and the freehub bearing. A simple double-hex hole has been found adequate by Shimano for years now, but they did try a spline first. The disadvantage of a hex is that it has a lot of flank pressure fro a given torque.
I'm prepared to hazard a guess. With that bolt, you have to find a way to apply enough torque in the limited space between the axle and the freehub bearing. A simple double-hex hole has been found adequate by Shimano for years now, but they did try a spline first. The disadvantage of a hex is that it has a lot of flank pressure fro a given torque.