With an 18x8.5 rim, you have a few options for tire sizes by mixing and matching the width and aspect ratio.
Technically an 18x8.5 could use the stock front tire size of an F Sport rim, 225/40/18.
Let's say you want a wider tire, but not a taller one, then we drop the aspect ratio and increase the width...255/35/18. The circumference is the same as a 225/40/18, but its 30mm wider (a little under 1.25 inches)
It will still clear as you're only adding a little over half an inch to each side of the tire, and also the +35 offset combined with the increase of 0.5 inches of the rim pushes the wheel outwards approx. 4mm.
So even though the rim and tire width were increased, there would still be an extra clearance of 4mm on the inside of the wheel.
At stock height there won't be any issues with clearing the fender either. If you were trying to bag the car and air out all the way, yes I would probably go with the 225/40/18 at that point.