I thinks the anwser is a no, but 18*8 with a 38 offset wont fit right?

 

No, it won't fit correctly. You can use your stock wheel/tire setup as a reference when doing the math.

Stock = 215x50/17 +55

One inch = 25.4mm

If you add one inch (25.4mm) to the stock wheel width, it means the inner and outer wheel will stick out 12.7mm each side(25.4 divided by 2).

Stock offset is +55

38 is 17mm lower than 55 so if you add the 17mm to the 12.7mm from the wheel. The outer wheel will stick out 29.7mm from the current position. Also, don't forget the sidewall of the tires, which will stick out another few mm.

 

Ok thanks, but a 18.7.5 with a 42 mm offset should work riht?

 

Yes, 18x7.5 +42 should work. However, it also depends on the size of tires and how much the car is lowered.

 

Ok sounds good, as far as tires i was thinking 235/40 's

 

which one would look better if lowered with Eibach Prokit?

235/40/18x7.5 offset +45
or
225/40/18x7.5 offset +45

 

The 235 will be nearly identical in OD to the stock 215/50/17 tires and the 225's will be just slightly smaller. I guess if you are trying to minimize wheel gap the 235's would be a better option.

Try this out: http://www.miata.net/garage/tirecalc.html