I ended up buying 4 used 215/40/17s and 2 of them were focked up so i just put the two in front end kept the same 215/50/17 in the back.

i left the tire spot and like a minute later the ABS/SLIP AND VDC OFF came on and then i went back and got it checked and he gave me an excuse and he said it would be fine. i then drove home and then tried going back out but my brakes were acting funny and heard one of the sensors going off.

did anyone replace with a smaller size in diameter and get the same issue? or know if this should happen? the customer service for infiniti is closed on weekends so i couldn't ask them. thanks for the info guys!!!