Originally Posted by DirtyDeeds
Wheel weight vs. foot print. The Focus is a heavier car than say a Civic and needs a wider tire. The problem with running 15" and 16" wheels is that there aren't a lot of tire size choices in the newer competitive rubber that will give you any advantage over that Civic that's running the same size tire. The alternative is to move up to a 17" wheel where you can run a bigger tire than can be stuffed into the wheel well of a Civic.
You might consider trying the following...
17x7.5 Rota Slipstreams with a 45mm offset. These can be found at zxtuner.com for about $140 per wheel.
Dunlop Direzza Sport Z1 Star Spec in a 215/40ZR17. These run $128 a piece at Tirerack. Just as much grip and heat resistance as the RE-01R's, but they have a stiffer sidewall and seem to do pretty well at full tread depth. The Dunlop's also tend to run wide on their sizing.
Throw on that Saleen suspension that Massive is selling for $500, some LCR street camber plates and kick some STS butt and still have a very livable daily driver.
Just my .02
And well worth it. But gee, I'm thinking of going cheap on the Focus. I think (that always gets me into trouble) that with the SVT suspension and the Pro-Thane rear sway bar bushings that I installed a month after I bought the car, it handles better than I can drive it. All it needs (again, IMHO) is better traction and the 17" wheels would give that to me. I try not to think about the money I have in my Miata with it's Konis, Ground Controls w/Eibach springs, Lenso 13X7.5 wheels and Kumho 215/50X13 tires, Racing Beat intake, Brospeed catback, big Addco front sway bar, Flyin Miata rear shock mounts and new 7" Torsen differential. With all that I am in no way competitive locally and would no longer dare to go to Nationals (I've been three times in the past).
Oh well, you've given me something to think about.