Hi guys i have a 2012 G37xS sedan. I wanted to get the Niche M158 and can't decide between 19s or 20s. Thinking of the 9.5 all around. Will the 20s clear? Planning on driving even in the snow so on hills or weird angles will it clear or will i have problems? also what offsets? Thanks in advance

 

Welcome to the site.
The 19s come in 8.5 & 9.5" widths
The 20s only come in 8.5/10/10.5" widths
Niche Form Matte Bronze M158 Wheels
The offsets for the 19x9.5 are +35, these wheels will extend out 33mm from where your current OEM wheels are (your OEM wheels are 18x7.5 +43)
Use this calculator when trying new setups
https://www.myg37.com/forums/tire_rim_calculator.php
That setup will look ok if you lower your G and run a bit more negative camber, At stock height the wheels will be right at the fender. This would be running 245/40/19 tires.
Check this thread for some various "square" setups.
https://www.myg37.com/forums/brakes-...post-here.html

 

What do you mean right at the fender? Wouldn't clear at bumps? What do you suggest I do if I'm trying to drive through out the year and live in city with big bumps

 

To get a visual, your new setup will be 1.3" further out than your current set. A good way to see this first hand is get a large paperback book, fold it open so you have 1.3" of pages, and lay that along the outside edge of your tire, this is how your new set will fit. You can also use a thick piece of foam or something similar. Just using a ruler in various places will work but not as easy to see how the overall fit will be.
If you want to run a 9.5" on a stock height G, a +45 would be a better offset, or you can run the 8.5" version of those wheels, they are a +35 offset so rather than being 33mm further out you'd be a much better 21mm.