OK. I see.
Let me express my understanding on what possibly going on with your moving pattern. I'm guessing of course!!! Please do not kill me if I sound stupid.
It is very possible that your new tires could change geometry and resistibility of your suspension system and result would definitely effect your steering system as well. If your wheel alignment is in the normal range and your steering ball joints properly set then I would say that steering system react on "road crown" more intensive than it was before when you had your stock tires. Ask you mechanic to inspect geometry of your suspension system and check upper steering ball joints (may be off-set adjustment needed). Also ask to check tightness of the steering stabilizer bar (I'm not sure if VX equipped with SSB). Just my thoughts on that.