Originally Posted by LWaB
Not quite correct, disc brakes (as commonly positioned on the fork) tend to push the axle downwards, as noted in the earlier link and unlike rim brakes.
That's true, depending upon the location of the caliper itself.
Originally Posted by 古強者死神
Seems like a logical solution is a slightly redesigned disk break where the pistons are on the other side of the radial axis, so instead of applying downward force to the wheel it will have an upward force... thus making it even harder to lose a wheel.
Yup, personally, I would mount it right behind or in front of the fork-tube like a motorcycle, rather than low and 90-degrees to it. This would tend to push the axle longitudinally rearward instead of down.