everyone in here is right, alignment, double check your wheel balance, and see if you have hub rings. you are right also in the you will feel more with less tire. also the 17's probably weigh a lot more that the stock 14's so you will feel imperfections in alignment, and wheel balance a lot more. the side wall of the tires on the 14s probably allowed for some play. if you get it realigned again i would do it with the 17's on.if thats the setup your going to drive on, thats the setup you need adjusted. i don't think alignments are under warranty on my car, except for their part failure? but simply changing a wheel and tire isn't going to void the warranty unless you wore out the wheel bearings or something.