Fellow Member (>400)
Join Date: Jan 2008
Location: Pismo Beach, CA
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The offset only defines where the wheel mounts to the hub. Has nothing to do with brake caliper/wheel structure clearance. That is up to the individual design of each wheel. Spacers can help because they move the whole wheel structure away from the brake caliper.
Personaly, I am using 17x8.5" Borbet alloys on my M635, with 235/40/17 rubber on all four corners. NO problems clearing my rotors, but the Borbet are designed with a short front lip, meaning the support structure is out away from the hub and brake calipers.