So I know this is probably a hard question to answer, but here's my plan. I want to fit either Eibach or Mountune (or whatever company) lowering springs to the car. I also wanna use the RE71R's on the stock 18" rim. is that at all possible?
@Dpro mentioned rolling the fenders. Would that help?
The stock wheel is a 17 inch. If you go with the stock size of 205/40/17 on the stock wheel and lowering springs I really doubt you'll rub on anything. I run a 17x8 and a Federal 215/40/17 on my autocross wheels and its wider, taller and more square than the oem size. I rub over big compressions on the street and autocross. Never really rub during daily driving. I'm also not
that low. Another thing to keep in mind is the actual dimensions of the tires themselves. Some tires are more square than others which can give you rubbing with one 2xx/40/17 vs another 2xx/40/17.
Example:
Falken 615k+: Height is 23.4 and the overall width is 8.4, tread width is 7.2
Toyo R888: Height is 23.5 and the overall width is 8.3, tread width is 7.6
Both are labeled as "205" wide tires however the R888 is a more boxy tire and has more tread width despite being a little more narrow than the Falken. 205/40/17 is a pretty vague number, the specs are going to determine rub or no rub. Long story short, if you don't want to rub get a 205 and you'll likely be ok when lowering. If you want wider and lower you may have to do some work to get them in there