I just put on a set of Sumitomo HTR Z III tires in a 225-45R18 on my 5-Sport this weekend. I am running a set of Mazdaspeed3 wheels and replaced the OEM Bridgestone Potenza RE-040 tires that were 215-45R18 sized.
My expectations - My expectations were not that high. I expected a signifigant decrease in steering response due to the increased sidewall width and tread squirm from a new tire. I also had low expectatinos of grip and comfort when compared to the Potenzas.
The reality - These tires really are great. Even though I went up a size, have a little more sidewall and the included tread squirm, I have not noticed ANY loss in steering response. They are a little quieter, just as smooth and cornering grip so far is as good or better than the worn RE-040's. These tires are also tracking much better and do not appear to be tramming as much as the old units.
Aesthetics - These tires are decent looking units. They have an asymetrical tread pattern so you can properly cross rotate and a nice finish on the sidewall. They give a nice, meaty look and help fill in the wheel wells.
So far I like them and may recommend them fully after a few more weeks of driving. They ar also available in a 215-50R17 which would be a good size for the OEM wheels on the 5.