What would be the correct offset?

[MJSpeed]

I'm thinking of going with this wheel but I'm unsure of the offset needed in order for the wheel/tire to be flush with the bodywork. The car is of original width, it is NOT a widebody.

The wheel sizes are:

Front: 17x7.5 (or 17x8)
Rear: 18x9

What offset do I need?

 

[Hapa88]

For a flush look:
17x7.5 +30 or 17x8 +38
18x9 +20

For a more conservative (safer) fitment
17x8 +40
18x9 +30

In either case I would recommend AGAINST the 18x9 for the rear. A 18x9.5 is a more standard, more typical fitment for NSX appications.

 

[MJSpeed]

…In either case I would recommend AGAINST the 18x9 for the rear. A 18x9.5 is a more standard, more typical fitment for NSX appications.

.
First of all thanks! I'm definitely going with 17x8 up front with 38 offset. My question is why not the 18x9 in the rears? What's the rationale?