Has anybody gone from the OEM 19s on their coupe to high-end 18s?
Did it improve the handling and steering feel? Did it improve traction?
What's the best combo? (i.e. wheel size, tire size, etc)

Thanks !!!!

 

You can easily maintain at least the same width of tire, so you shouldn't have all that much difference in handling or steering feel provided you use the same type tire (i.e. high performance summer to high performance summer and not high performance summer to a "touring" type tire).

However, you will most likely notice a somewhat smoother ride due to the larger sidewall.

 

Any advantage to using a 18 as opposed to 19 inch wheel?
Obviously weight, though I"ve noticed most tires are comparable.
Ride due to taller sidewall.

I'm looking for more steering feel.
Additionally, I noticed that the Z car only runs 18s from factory, I'm wondering if there was a compromise when they went to 19s