Wanting to Change from Staggered to Squared setup, And Sasnuke has been Awesome and very informative about What could fit and what size tires. So I wanted to see if any 3IS RWD or IS200t RWD with F-Sport Stock suspension has done 19X9.5 in the front and back Or would I have to stick with 19X8.5 All around. Also What Size tires are most of Squared setups running.

 

Yea I understand that, But from what I've Heard Is You can do 255/30R19 Squared and that's what comes stock on the rear.

 

@Sargon I think I'm not quite understanding what you are trying to say. Why would the rear tires be smaller? And why would the front tire size be limited by the suspension? I mean you can only put as big a tire that can fit the rim...for example, you can't put a 285 on an 8.5 inch rim, and a 255 on a 9.5 inch rim will fit the front fine with the right offset.
If anything, the front tire height is limited by the fender/fender liner. The rear you're limited by the fender really when it comes to tire width. Although that is really simplifying it as there are a number of factors...rim size/offset, and tire size.

 

I think what he means is if you want to go for a square set up, from stock rear (255/35/18) you would be going down in tire size 255 -> lower number and 35 -> lower number because the front most likely can't support 255/35 tire. So you'd have to find out what would fit in the front which I would assume might be the limiting factor since it already has smaller tires up front. That's what I took away from that.

I've been meaning to ask you though, what would be a square set up for a 19x9.5 +35 offset tire size?

 

I can see what you mean, I guess what I'm looking at is the F Sport rear rim is 18x8.5 +50 with a 255/35/18 tire, which is 25 inches in diameter. If you increase the rim to a 19x9.5, and use a 255/30/19 tire, the tire diameter is still 25 inches.
What really shrank is the sidewall height when you went from a 35 to 30 aspect ratio...so technically the tire is not smaller, it's actually the same size (diameter).

A couple members have 18x9.5 with 255/35/18 on the front of their IS...which would mean if you convert that to a 19 inch rim, it would be 19x9.5 with a 255/30/19 tire.
Because the width of the rim is wide for the front, the offset is crucial...ideally it would be between +33 to +38. For the rear an ideal offset would be +38 to +42.
It would appear that the simple solution is to get a square 19x9.5 +38 with 255/30/19 tires...the problem is few offer +38, where you'd be more inclined to find +35.
The +35 would work on the front fine, the rear becomes an issue. Stock height might be ok with a narrow fitting tire, as not all tires are created equal, but if you're lowered some have had rubbing and some have not.
It's like 20mm spacers on the stock rear F Sport rims...some have rubbing, and some don't, so a 15mm spacer is more popular cause it won't rub regardless of tire brand...assuming in all causes the tire size was the same.
Really when you get into those last couple mm's of clearance is when you make it or break it...in this case, don't rub or rub.

 

Thanks a lot!

 

19x9 +36 225/35/19 Should work well ... anything bigger you will rub,. You want to make sure the front fitment is spot on, 19x9.5 will not fit without stretched tires..

 

@TOPENDMS I would agree that 19x9 is a much easier fitment with more options for rim and tires selection.
However I'd have to disagree about the 19x9.5 fitment. A couple members have 18x9.5 +38 on the front with 255/30/18 tires lowered. Dimensionally it's the same as 19x9.5 +38 with a 255/30/19 tire...and even by the manufacturers recommendation a 255 is still an appropriate fitment for a 9.5 inch rim. True it is the maximum fitment recommended for 255, and will likely have a slightly stretched look, it's still perfectly safe and not the unsafe stretched we see on other vehicles just to make rims fit.