I have Rota Gravel 18 x 8.0's on my 06 WRX with 225s on them and there is a small bit of the rim exposed. Picture is below and you can just make out the exposed part. I would expect going 8.5 would expose that little bit more.

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[I]and then we discovered it wasn't the Robot King after all, it was the real one. Fortunately I was able to reattach the head.[/I]