When the 3IS came out, I remember that the tires didn't do the car justice.
I tried to look up the specs, but it was confusing (to me).
Do I recall that the 2014 base came with square 225's?
When did the 255's arrive? Only on Fsport? Only on 350?

I like the looks of the 255 rears on my 2017 IS300!
Changed my whole opinion of the car.

 

On the F sport wheels.

 

All of the 3IS F Sports, regardless of engine, come with the staggered wheels...225 on the front, 255 on the rear.

 

My 2015 IS 350 non-Fsport came staggered, but it is a Canadian model with the Executive package (similar I think to the Luxury package in the US). Only if I had bought a base model would I have seen the 17" square setup. I like the look too, but the resulting understeer is noticeable and the tires can't be rotated, so I went square with my winter wheels.

 

Non F sport 2015 IS 250 came with 225 front 250 rear.. all IS's have that set up.. the luxury package wheels I have and the F sport wheels have the same diameter and offset.. but mine are luxury package wheels.. can't speak the same for the 17's that some IS's come with

 

Idk about the 250 but definitely the 350 all come with staggered setup regardless of package / F-Sport.

I feel like I've seen 250s with square setup.

 

I think region will depend on the exact packages and sizes available.
So far I think we've confirmed for sure that there is a 17 inch square package that comes with 225/45/17 all around.
Also all the F Sports comes with 18 inch staggered with 225/40/18 front and 255/35/18 rear.
There also seems to be a non F Sport 18 inch staggered setup...assuming the same tires as the F Sport rims...personally I haven't looked at a 3IS non F Sport close enough to confirm or deny this package exists.

There was also a 3IS250 16 inch square setup that I don't think we got in NA. It's in the Owners Manual in the tire section at the back in case anyone thinks I'm crazy lol
Of course it will only fit a 250, as the 16 inch won't clear the big brake caliper of the other models. I was actually using those specs for my winter wheels until I upgraded my front brakes to the bigger stock calipers.

I'm not sure if there is a 18 inch square setup available for 3IS...of course the model lineup in Canada is less than the US, so I leave room for all possibilities.

 

For the US market, it's actually not too complex.

Staggered wheels are included on the following:

• IS 350 base gets an 18-inch staggered setup with 5-spoke wheels.
• All F Sport models get the gray 18-inch F Sport split-5-spoke wheels, which are staggered.
• IS 300 RWD or AWD might have the optional 18-inch 20-spoke (AKA "mesh") wheels, which are staggered.