Stretch is NOT good if you road race usually you want a very square setup and thus 215/40/17 would go on a 17x7 . The sidewall on a stretched tire becomes flexable which helps depending on your driving. Quite a lot of people that drift like having stretched tires and some dont... give it a try I bairly get a stretch with my 215/40/17 continental sport contacts on my 17x7.5 so 8's will be good.
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