Have been doing search on this subject. 1: ZR rated tires are available for both wheel sizes, tires for 18" are more $. 2: Considering trying to maintain stock tire height (245/50/ZR16) of ~25.75 inches, both will require lower sidewall profiles. 3: Lots threads seem to deal with esthetic issues,i.e. driver preference.

My questions
1: is there much "seat of the pants" handling difference between the two sizes at high speed, acceleration, and cornering?
2: are there any safety concerns to be aware of between the two sizes at high speed, acceleration and cornering.
3: Is a tire width of 255 about the max to go when considering all 4 tries being equal width.
4: What is the maximum overall tire height that can be had considering stock wheel wells/fenders/suspension set-up.

Thanks in advance

 

I have 18x9.5 C6 Wheels at all four corners. 275/35/18 tires.
1) The only diffrence I felt going to the 18" were harsher bumps. This was expected because I have 2 less inches of rubber.
2) With bigger wheels, you always have to keep a close eye on your tire pressure.
3) No, I have 275's on the front and the back with no issue what so ever. This is also the size that came on stock SS's and Ws6's.

 

Some Auto-Xers have been known to throw 315's on at all 4 corners...personally I have 275/40/17 fronts and 295/35/18 rears, not TOO much of a difference but it is slightly harsher I guess. Cant help you with high performance handling stuff, sorry.