We installed a take-off set of tires from my BMW 335i. Those happen to be sizes 225/40R18 and 255/35R18. They fit the car easily, without any rubbing. If I was buying a brand-new set I'd probably go a bit wider, to a 265/35R18 in the back and a 245/35R18 in front. I think those would fit without clearance problems. The rear I'm sure is an easy fit. The front might be a little tight to the strut -- the spring perch sometimes gets close to the tire when you start going to a wider size. Nothing a small wheel spacer wouldn't take care of.
In fact, I am thinking I might try some slim spacers just to space this set out a few more millimeters. There looks to be plenty of room to the fenders. The +44 offset is a good bit more than most aftermarket wheels for this car, although I definite prefer higher offset to lower. You can always space a wheel out using spacers. There's no way to push a wheel in if the offset is too low.
As usual, we secured the wheels to the car with McGard SplineDrive lug nuts.
Weight on the wheels is 21.2 and 22.1 pounds for the 8.5" and 9.5" widths, respectively. That's only a couple of pounds heavier than the stock 17x7" wheels (at 20.1 pounds).
The RKR comes in other colors, including black and "Hyper Blue," which is a very vivid deep blue color. I thought the Hyper Black looked classy without being too loud, but I confess I'm curious to see what the blue wheel would look like on our car.
Products mentioned in this post: Rota RKR wheels, McGard SplineDrive lug nuts.