Well it just seemed like you were asking a lot of vague questions without much information behind it and wanted specific answers. I mean it sounded like you had an intent with where you were going, but never really went anywhere with it? If you're looking for a blank slate plan, then that's one thing, but it seemed like you had already made some choices.
I mean if you really want a suggestion, then I would say get NT03's in 18x10.5 + 30 or whatever the lower offset is, at all four corners. Run 285/30/18s all around. Make the body fit the wheels. Buy a suspension setup from me because it will be valved to the car and matched with exactly how the car should be. And then start your alignment at around -1.5-2* camber in the front -1-1.5* camber in the back, a little toe out in the front, a little toe in for the rear and get your front caster even while maintaining the camber settings that the car needs.
With that setup, plus aftermarket suspension arms or at least new bushings. The car will handle awesome, look sweet and just be pretty nice all around. Just get brakes and you can take it out on the road course all day long and then drive it home from the track.
As for your other comments, I'm pretty sure racing gear n1 are just another cheap asian coilover. Can you prove that they aren't? Any kind of data on them or any kind of specs? Or even what are the spring rates, because a lot of the cheap companies like to pick spring rates that really don't work well for the car, especially lowered.
And I don't hate everything from japan, but it's not like that would include the racing gear coilovers. I really doubt they're made in japan. Most likely china or taiwan. And it's not a construction complaint anyway, I'm sure they're strong enough to not break. It's a valving concern. Most JDM and asian dampers use really old piston technology (if you could even call it that) and crappy shim stack design. Not to mention the adjustable ones and there very poor adjustment method design. I mean I took apart a silkroad damper a little while ago, and cheap mountain bike shocks that I had used on an FSAE car in college were built better and more complex than the silkroads. I'm not saying you need all kinds of bells and whistles to make a damper work well. I mean look at Bilstein, a good, simple design that works well, but it's the very good basic design principles that really set it above. The piston is designed well, the shim stacks are thought out. It's not some mess or cheap parts thrown together with some fluid.
But what I meant about the Bilsteins that you have, is that with an off the shelf damper, unless they were really modified or are in a totally different body, will not let you get the car to a proper ride height for racing. You can get the valving right and they can work with all kinds of spring rates if you want to, but they're limited by the size of the shock body.
As for something better, it really depends on what you really want and how much you want to spend. I obviously would recommend one of my setups because I know they work, I know they're valved right and I know that all the specs match the actual car they're going on. But they aren't cheap, at least the ones based on motorsports dampers. You would be looking at $1750-2400 for the more basic motorsports packages.
For off the shelf stuff, again, it depends on what you want. You can run the Bilsteins or even Koni off the shelf stuff with different spring rates and have a soft, dual purpose suspension. It will probably be better on the street than it is on the road course, but it wouldn't suck on the road course. As compared to a custom valved motorsports setup which would be awesome at both, although a little rougher on the street than an off the shelf setup, but still not much at all.
And then there are asian coilovers. I don't like them, I have lots of reasons. They just can't seem to get anything right. They ride rougher than they should, the spring rates aren't always right or even close sometimes. The adjustability sucks and you can never get them dialed in right. But they can look pretty.
Well if you don't want to look at what other people are running, then how do you want the wheels to fit. I ran 9.5+12 with my steering spacers and the car low both at drift events and on the road course and it never rubbed. This was just with rolled fenders, nothing pulled and a not too agressive alignment. I also only had a 235/40/18 on there, and there was room probably for a 245 with no work or a 255 with a little pull. So you can use that for a baseline and then just do some math and you can figure it out.
You should be able to fit the setup I mentioned in my first post if you aren't scared to pull a little more on the fenders. But it might fit with what you have. I'm talking about the +35, not the +18 even though the +18 might work. But again, it depends on alignment and ride height and spring rates. If you have stiff springs, you can go low and not have to worry about the tire hitting the chassis. If not, you have to raise the car.
I would really suggest looking around more. There are lots of threads in this section that talk about coilovers and spring rates and valving and what works on these cars. There is a lot of info on wheel fitment. And even if the person isn't driving their car hard, you can at least see how the wheels fit on the car. Or you can just ignore all of this.
