ALPSTA

iTrader: (3)

I am buying new wheels for my car (18x9.5 +45 255/35 front) and they come in two different offsets for the rear:

18x10 +40
18x10 +42

I will be running 265/35 tyres this time but I might want to try 285/30 in the future (it's a small possiblity though). And I am ok with minor fender rolling.

I've noticed members using +38 with no problems and in some cases with 265 tyres they looks narrower and more inside the fender then +42 or more with 285/30.

According to the wheel size calculator +40 is 0.07" inside the fender and +42 is 0.15 inside the fender. According to the will these wheels fit calculator +40 won't fit and +42 will.

I think I'll buy 18x10 +40 since the difference is minimal but just wanted to ask you guys and confirm before I made the purchase. Speak now or forever hold your peace

Rxmfn7

iTrader: (4)

As you probably already realize, 2mm isnt really going to make much of a difference at at, especially in the rear. Youd most likely never notice the difference between the 2. Id go with the +40, and also Id be running the 265/35r18 up front and the 285/30r18 in the rear with the sizes and offsets that you listed. Ive personally an those sizes with about those exact offset with no rubbing issues, but it will of course depend on your suspension and ride height.

ptrhahn

iTrader: (9)

Get the +42

I have that exact size, w/ a 275/35/18 Toyo T1S. Just for fun I put in my 5mm rear spacer, and some tape on the fender lip and went for a short drive. I couldn't hear any rub, but when I came back the tape was all worn off.

If you're thinking about going up to 285/30/18, and since there is some variance in size between different manufacturers, those 2mm might end up being pretty important some day.

ALPSTA

iTrader: (3)

I went through my RX7 photo library before and looked at most of the members cars to see which look I liked the most. For example Goodfellas and Alex Rodrigues are running +38 with 265/35 and it looks quiet good. On the other hand while Cabaynes' car is also looking very nice, his rear wheel sizing wasn't for me. He is running +43 with 285/30 and his wheels have the illusion of looking level or over the fender line compared to a +38. I don't know if it makes sense but for the reason I mentioned and 255F/265R being a happy medium between stagger and square, I decided to go with 265/35, at least for the first pair.

ptrhahn

iTrader: (9)

^^^

Note, unless the wheel manufacturer changes the center/pad, you won't see a visible difference between a +40 and a +42... the look will be down to the particular wheel model, tire model, lowering, etc.

Here's how mine sits:

MR_Rick

iTrader: (7)

I run 265s on the rear on 18x9.5 with 40mm offset and there are no issues. Actually thinking adding a 3-5mm spacers to make the flush. On my last FD I ran 18x10 with 44 offset on 275s. no issues there either.

ALPSTA

iTrader: (3)

I think I'll go with this set-up:

F: 18x9.5 +45 255/35
R: 18x10 +42 265/35

Like ptrhahn said, that 2mm may be the deciding factor between rubbing/fender rolling or stock.

I think with +42 I may not even need to roll the fenders at all and I can always use 2-3mm spacers if I want in the future. Having said that I could have the back of the +40 machined 2mm to have the same effect if it rubbed