Look at the Bridgestone RE11 as well. I am on a 205/50-15 RE11 now, and it is the fastest street tire I have ever run on my Focus. I am in love with the shorter gearing, decreased rotational inertia, and the FEEL, oh the feel. They give you an insane amount of information when you approach the high, but very consistent and predictable limit. My previous autocross tire, which I'm still running on the street, and frequently doing direct swap comparisons with, is a 205/50-16 StarSpec. The StarSpec is known to have a somewhat vague feel, so I wasn't surprised to find the RE11 feels better.
Oh I guess to validate this rave RE11 review, I should quote+link this thread:
Originally Posted by mellephants
The tires that I have chosen to use for autocross racing, in order, are
On a 16x7" wheel: 225/50-16 (24.86", 4.43") BFGoodrich g-Force Sport
On a 16x7" wheel: 205/50-16 (24.07", 4.04") Dunlop Direzza Sport Z1 Star Spec
On a 16x7" wheel: 225/50-16 (24.88", 4.34") Hoosier A6
On a 15x7" wheel: 225/50-15 (23.86", 4.34") Kumho Ecsta V710
On a 15x7" wheel: 205/50-15 (23.07", 4.04") Bridgestone Potenza RE-11
On a 15x7" wheel: 225/45-15 (22.97", 3.99") Hankook Ventus R-S3 (I have not used this tire yet)
Note that I am currently using the 205/50-15 RE11, but I am going to try the 225/45-15 RS3 or the 225/45-15 Z214 next season. I am going to because the size is both wider and shorter, and I've heard nothing but praise for both of the Hankooks.
Pricing on the RE11 is a lot higher than the competition, but they will last almost twice the number of competitive events than, say, a StarSpec.
Bridgestone Potenza RE-11
205/45R16 87V $177.00 (ea.)
225/50R16 92V $145.00 (ea.)
Oh, since I'm on the subject, I cannot give a fair review of the 16" Hooser vs the 15" Kumho. They were both quite fast, but I ran them a few months apart, with different car setup, and significant driver development, in between.