2012 Black SX Prem. & Tech.
Agreed - I noticed a difference on my 2012 SX (sport suspension) when I went with a slightly taller sidewall than stock, the ride quality improved. After that experiment, I kept re-ordering my tires with that slightly taller profile.lower aspect tires, etc. all affect ride significantly. I use a 17" tire in the winter and the ride is significantly better due to the taller sidewall. Remember certain kia models have a sport tuned suspension which is inherently stiffer (Spring rate, shock valving, etc. al).
Current taller profile: 225/50-18
Normally it would be stock shorter profile of 225/45-18
With the taller profile you get roughly 3% larger circumference, so it's not a huge difference, but I remember how it felt "better"? I never studied how it affected fuel economy, but I'm guessing it moved the "sweet spot" cruising speed by around 3% up or down???