Hello,
i'm Carlo from Italy

i have an Infiniti M30d S Premium with 4WAS system (same as M37 but is 3.0L Diesel)

i want to change the stock wheels to the Axe EX20 Gloss Black Mirror Polished

OEM wheels are 20x9j

Axe Ex20 comes with two variations = 20x8,5j and 20x10j

the problem is that here in Italy for legal reason, you can't mount tyres different to OEM stock certification, so tyres has to be forced 245/40 R20 , can't change

now, my question is:

can i have problems with 4WAS (stability) or 245/40 stretched tyre problem to match 10j if i mount:

front: 20x8,5j 245/40
back: 20x10j 245/40

???

i want 10j on back just because concave style have better look, 8,5j on 4 has no problems for sure, just want to know if i can go with 10j on back without problems

thanks to all for help!

Not an expert but that should work fine. It may look odd though since the front will have a more verticle sidewall and the rear will be more angled. I'm sure some smarter than me people will chime in and help you out.

If I'm understanding correctly you cannot have a different tire size even if the rolling diameter is the same as the factory specs?

You can certainty run 245/40/20 on staggered wheels but as Deb mentioned it will look odd..your rear tires will be stretched, the fronts will look slightly bulky.

that's right, for legal reason here in italy you can't run different size tyres from factory specs

so, front and rear tyres has to be 245/40/R20

i want to put 20x10j on rear just to have a better look because the Axe Ex20 wheels are concave

245/40 on 10j is too stretched ?

no problem with stability? no problwm with the 4 wheel active steering system ?

Man, as much as the US is not perfect, we have to sit back and appreciate our liberties once in a while.

Back on topic, here is a link I've used for visualization in the past: https://tyrestretch.com
Wheel width, tire width, aspect ratio, wheel diameter. Beauty is in the eye of the beholder as to whether that is too stretched.

And no issues that I can think of with regards to the stability systems. Just watch the curb/kerb if you parallel park often.

already look at tyrestretch , the problem is that there's no pictures for 245/40 on 10j

you mean take care on parallel parking to don't damage the rim that is exposed , right ?

That's what he meant.

Is it possible to get all 20x10 wheels?

Yes, minor fear of damaging the exposed rim. However, there are tires that are made with lip protectors to help with that.

And sorry, I hadn't checked through that link myself at the time. I found a thread on a Lexus forum showing pictures of 235/35 series tires and they looked a little too stretched for me although some reported long periods with no issues.
Here is another visualizer I use:
http://www.wheel-size.com/calc/?wheel1= ... 0mm&sr=0mm
I don't like the tire contact patch being that much narrower than the wheel.

Although not ideal either, I would be more comfortable playing with the offset rater than tire bead engagement. How about you get the 8.5" wheel with a lower offset? High offset = wheel close to suspension components, low offset moves them further. Since the width will remain the same, I assume the spokes with sink in a little more in the center... if you have to stick with the Axe ex20.

oem stock sport pack wheels = 4x 20x9j ET40 (right?) with 245/40

i will run 4x Axe EX20 20x8.5j ET40 with 245/40 tyres just to avoid any kind of problems

by the way i found that 8.5j is an overall perfect match for 245/40 tyres , doing better tyre contact than stock 245/40 on 9j

i think to live the same without posterior 10j concave effect...

OEM sport wheels are 20x9, et 43

-> 4x Axe EX20 Gloss Black Polished Face 20x8,5j ET40 with 245/40 tyres gonna be fine