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I have a 2010 base which came with 245/40R18's on the front and 285/35R19' on the rear. I changed to 265/40ZR19's on the front and 345/30ZR10's on the rear.
When I bought it there were 305/35ZR19's on the rear.
I'd say not necessarily, but one wouldn't hurt if you have some tracking planned with those tires...
If the old tires wore evenly, the car goes straight down the road, and the steering wheel points straight ahead when you're going straight, moving to a larger size shouldn't require any different settings.
Keep an eye on the tire wear, that will let you know for sure.