Just be sure & keep front/rear tire diameter differential to a minimum.
I've always heard max 3%, but around 2% is more common.
Too much & lots of warning lights will be lit up on dash ( Christmas Tree effect),,,so keep that in consideration if you stagger tire diameter.

If my maths is right...
Percentage difference 26" -25" diameter

(((26-25)/(26+25))/2)*100 = 1.07%

1.07% shouldn't be noticeable then...

Thanks for the input

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OH MY GOD

Following that exchange between jhammond and pumpgas is making my fuckin head hurt.

ARGH

1) Regarding the wheel diameter difference:
255/35/18 is 25 inches
265/40/18 is 26.3 inches

That is a 1.3 inch difference. 1.3 inches is 5.2% of 25 inches. You are likely to experience warning lights due to this difference.

2) Why your setup looks and fits different than this setup you're looking at:
Thats a 265/35/18. You bought, apparently because they're cheap, 265/40/18. Thats obviously a taller tire AND the linked car has -2.4 deg camber, which solves the rubbing issue

Combine lack of camber and taller tire = rubbing more than that guy.

Your car naturally gains negative camber as you go lower, but the correct way to do it is to buy adjustable suspension parts, roll your fenders, and then you can run whatever wheels you want.

If you want a cheap fix, just get the 265/35 and pound your fenders

but you really should just buy the fukin SPL and save yourself future headache

You'd most likely have no problematic symptoms other than fitment. The problem comes with the rolling speed of the rear tires are faster than the front. In that case ABS and traction control may fail, abs would start fluttering or release the brake pressure, traction intervention would be way more intrusive. With the rear tires larger than the front, the RPM of the rear is slower.

On most approved ABS systems, the difference is 4% at 60mph, as tested by many, if not all major manufactures.

Yikes! Can't thank everyone enough. Just bought spc front upper control arms. Before you guys freak out, I have read the countless accounts between spc and spl.. I truly believe spc will be enough for what I am capable to do with the car. Since my rears fits fine, I'll be leaving it as is.

My goal is to not roll my fenders forgo thread life, bc stance life. Anyways, I do believe the -2.4° will be good for handling provided it was taken from track spec...

I'll be posting finished product over in 18s thread and I'll edit a link here.

Again, thank you all for the input and care. Awesome community! Another reason I bought the Z, the helpful community of z owners.


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I failed to mention that the caveat of this inverse wheel speed, is that ABS and Traction control may fail to properly engage in the adverse scenario as it wont detect a significant wheel speed difference unless you lock the wheels. So you will be much more prone to locking the wheels and then ABS might kick in late and cause some annoying sensations, certainly in wet situations.

TC may allow more wheel spin as well, which may sound fine in a straight line, but not so much through a corner. In such case you may want to drive with TC off. The problem with incorrect TC intervention isn't oversteer, but understeer and snap direction changes when TC finally engages, which in almost all cases is much much worse. Going *** in to a crash is safer than nose first. Of course there is much more to this "scenario", but those are the potential drama's.

The other issue is the decrease in caster, adding to the already low caster angles, the steering will be even more loose then roll into annoying low speed understeer as the rear wheels drag through the corner. A immediate correction here would be to add toe-in front, more positive camber in the rear (+-.05)

Sorry for the preaching.

hello!

Thinking about running a square setup.

Will this work: 18x11 +14 285/40 ?

Rear is easy
Fronts are hard

Front upper arms to get around 3 deg camber, plus roll fenders and trim some liner. Also trim the front bumper tab

I have 18x11 +18 square and test fitted the fronts with NT555R's in 305/35 and I had no issues with rubbing or grinding up front. My front camber is at -2.6. Those 285's are gonna be stretched quite a bit on an 11" rim.

Why dont you go 18x10.5 instead? As Hotrodz said, Those 285 will be really strectched

I went back and forth on a 10.5 +22 but I wanted a true square setup so after I test fitted with 305/35 I decided to go stay with the square setup. I will be running 315's!

I'm not a track guy; but seems the 27" tire may be a bigger issue than the 285 width.
Hotrodz says 305/35's didn't rub on his & they're roughly 26.5"...seems like a better fit than the 285/40's on the 11".
But 315/30's on all 4 corners is gonna take some whp/tq to get around the track.
:)

Nah

Had 275 27" up front before on 9.5" +25 and no rubbing. There's going to be some variation depending on wheels, tires, offset of course but unless a guy is running something like +40 I can't see there being an issue

The wheels specs are 18x11+14's on all 4 corners; that's a tad on the aggressive side w/27" rubber.

"really stretched" . . . c'mon

It won't be square, but dont act like its a fuckin 215 or something. I'm running 275 on an 11, its fine