I ran a set of 225/50ZR-15 this past weekend at Lime Rock. The reason I went with the taller tire was because I wanted a little more speed since I was running out of RPM in the wrong spot. The tire fit fine on my MK3 with 10mm spacers in front and smaller spacers in rear..maybe 5mm maybe a little bigger. I did not measure them.
The taller tire helped a little bit with th RPM but I think I should have gone with the 225/45ZR-15 with the shorter sidewall. The taller sidewall did not provide as quick a response for turn in and not enough of a crisp clean feedback. They felt a little muted compared to some of the other hoosier combinations I have run.
I think the best combination is going to be the 225/45 and then change the final drive to something else.
I like SSR rims. They are very light weight.
Thats my .02
Beran
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Right, the 225/45's are definitely desirable, but as mentioned, they increase the side wall angle from the already bad angle of the 225/50's. The bad angle will increase your shoulder wear, and counteract your goal of increasing the stiffness/feedback. I am running 225/50's, but on 14" rims, which is the same ride height as the 225/45's on the 15" rims, but keeps the better (but still bad) sidewall angle.

However, 7" rims would work perfect w/ those 225/45/15's.