hey i have 275/40/18 on my rear g37 18s and i also have tein s tech lowering springs. which spacer would be best to look poking out from behind the car? im guessing that would be a flush fit with the fender or sticking out a little bit more im not sure so im asking for help

 

25mm. You may rub though but it'll give you the appearance your asking for.
20mm is probably the safest and cleanest look though.

 

yea i tried 30 mm today and that was horribly off felt like it stuck off the car a good 2.5 inches. so im guessing 20 would be best? how do you achieve that look then? coilovers with neg. camber i assume? theres no way with some spacers?

 

Your tires are too fat for a 9inch wheel. A 225 would provide a little stretch and allow your wheel to poke.

 

Check out some of PCasey or Doggy's threads/pics. Apparently they know what they're doing. :P

 

I have 20 MM on my X Coupe( Stock 18's ) and the look is nice and flush.

 

20mm.....

 

I have 20MM F and 25MM R on my stock 18's. Looks good (nice and flush) and no rub.