Banked Curve at the Magic Speed and Angle (2/3)

The reason is that breaking up the centripetal acceleration is really hard. It's purely in the r axis, which is what we'd usually call the x axis in the classroom, and if you tilt your x axis now you've got a centripetal acceleration in 2 dimensions (which is no fun.) This diagram should help you see how to break up Ffr and Fn

Done