Workmeisters eh?

Now we are talking.
If i remember correctly...they have some in 18x8 +53mm and 18x9 +60mm. Sweet offsets!

 

Here we go again.
Lots of GOOD information and a tad bit of MISINFORMATION.
First off, one has to look at the definition of "fit" and how it relates to tire/wheel outboard distance. Some folks feel ANYTHING that deviates outboard from the OEM tire location (or edge, if you prefer) is an incorrect fit and you'll hit the fenders. Over time (and the plethera of folks who have proven otherwise) we now know this is simply not the case. You can run wheels with low offsets so long as your wheel width isn't so wide as to push your tire/wheel edge to unacceptable levels. What is unacceptable depends in large part, to your own visual but more importantly, what your intentions are with the automobile (lowering) It also depends a great deal on the diameter of the tire. Assuming you will remain within a tenth of two of stock 24.8-inches, if you want to run an 18-inch wheel in front, you'll want to keep that wheel's width to 7.5-inches maximum. The reason?
If you ran the lowest width 18-inch tire available (215mm) on a 8-inch wheel in front, assuming like-OEM diameter, you would go outboard 1.5-inches. So not cool and thus, fairly makes a good case that an 18-inch tire in front with a low offset is not going to work with your 8-inch wide wheel. Hell, even If your wheel was 7.5-inches, a 215/40/18 tire would still be 1.3-inches outboard. Again...a poor choice. You have to play with the numbers (keeping in mind stagger between front and rear tires) to make this low offset wheel mumbo-jumbo work. Let me give you a perfect case. I chose a wheel that was offered in both 18x7.5 and 17x7.5 with a ET40 (offset). On a 205/45/17 tire (24.3-inches in diameter), the fronts went 1-inch outboard. As you can clearly see by the pic, this isn't a problem (or rather, hasn't been) with hitting the fender because the tire's diameter decreased by half an inch. I currently can put three fingers in the gap between the tire and wheel well. With that being said, it is my opinion that apart from visuals which change from one opinion to the next, you shouldn't go beyond a one-inch outboard deviation from OEM tire/wheel edge location.
The problems (among many) that you're encountering with that initial wheel choice is you're attemping to use the same width wheel on both axles and what that does is limit the ability of you to stagger tread width. Most wheels have a measuring width variance of 1-1.5-inches. For instance, a typical 225/40/18 tire would have its measurements taken while mounted on a 8-inch wheel. The variance in mounting specs for that tire would typically allow you to mount it on a wheel anywhere from 7 inches to 8.5 inches wide. Bear in mind any deviation from the measured wheel width will affect the tread width as well (.2 inches or 5mm for every half inch deviation). For instance, a 225/40/18 Parada (eeks) tire mounted on a 8.5-inch wheel would result in that tire's tread width INCREASING by 5mm. If that tire was squeezed on a 7-inch wheel, it's tread width would DECREASE by 10mm, making it even narrower than it already is. Getting back to your scenario, the widest sized tire you can fit on an 8-inch wheel with an aspect ratio of 40 would be a 245/40/18 which would result in a tire that is 25.7-inches tall. To keep a stagger of tread width, you might go with a 215/40/18 in the front which would more or less match the OEM diameter. However, you're an inch taller in the rear. Not acceptable. Forget the 245/40/18. How about a 235/40/18? That's closer to OEM (25.4-inches) and would be an acceptable variation with regards to the ABS but alas....do the math on the handy tire/wheel calculator (any google search will take you there) and you'll find yourself going 1-inch outboard with that sized tire/wheel. My 225/40/18 on the Velox 18x7.5 (ET40) pushed things out by .5 inches which puts the edge of the tire just under the wheel well but not DIRECTLY under it (if that makes any sense). I have a two finger gap which leaves plenty of room and I've never EVER hit the wells or even come close. I weigh 235-lbs as well. In fact, I could probably drop the car one-inch and be fine according to my head mechanic.

The point being, with all the numbers crunched, you have a bad combo all the way around. The only way low offset wheels can work is you have to:
1. Stagger the wheel widths and usually unless the wheels have lots of width options, the only way to do that is by choosing one wheel (front) one-inch smaller than the rear. Many times you have the option of a 7.5 or 8-inch wheel in the rear and that same wheel in a 7 or 7.5-inch width because its one-inch smaller (say, 18 in the rear, 17 in the front).
2. Because of the enormous tread width of the OEM S0-2, when you use a tire/wheel calculator, do NOT input 225/50/16 if you want accuracy with final results. Input 245/45/16. You're not concerned about aspect ratio at this point, only a proper size which indicates just how wide the OEM tire size is. This is why my 225/40/18 tire on a very low offset (40) wheel only went outboard half an inch...because the tread width on that tire is .6 inches narrower than the Bridgestone S0-2.
Most of the replies to your first post were correct but low offsets, in of themselves will not kill your fenders. With YOUR choice of tires, you couldn't drop the car but you wouldn't hit anything either. The biggest problem would be how horrible it would look. If you're willing to work with it though, you do have an option. Like I said, I've gone from 24.8 to 25.1 in the rear with the tire going half an inch outboard and still have two fingers of gap with NEVER a problem. Schatten is correct that you are not going to find any tire manufacturer which offers BOTH a 215/40/18 and a 245/35/18 so you're out there as well.
If you're dead set on this wheel, here is my recommendation:

See if it's available in a smaller 17-inch size with hopefully, a narrower width. If it is, go with a 205/45/17 or 205/50/17 in front and a 225/40/18 in the rear. If you go wider, you're approaching a one-inch outboard look and you won't like it. Half an inch is ok. With the tire stagger so close, you'll want to spend some time on some deserted roads getting familiar with oversteer but with enough practice, you shouldn't have any problems. The increased tire track you will have going outboard on both sides will help to offset the decreased tread width. So much of the feasibility of this depends on your driving style, experience and more importantly, how hard you want to push the car. If you plan on racing it, forget everything I've said...my recommendations are for "normal" operations only.
To sum it up, the goal of any aftermarket tire/wheel combo is to maintain as close to OEM dimensions and stagger as possible however there is more flexibility than others might have you believe. You just have to be honest with yourself. Anyone not carving canyons would be hard pressed to tell the difference between a well thought out staggered combo with a decent tire and a stock S2000 running on OEM sized replacement tires. I won't use the gumball S0-2's to compare because they are in a sticky league all their own. I've run on the same roads with this combo that I did with the OEM's and the only differences I've noted are the Ecstas's, while not nearly as gummy, communicate better. They'll wag, but give you lots of information in the process and never bite you in the rear. You'll know where your limits are well before the car starts to get dangerously loose. I would think a tire with an even sticker tread though sized the same as my current combo would be even nicer. Maybe the Kumho MX's are up next?

 

jesus man, brilliant reply