D00ds - After looking over this forum for the past 30mins, I can't seem to find what the max acceptable tire width is for my OEM rims on a 09 G37xs Sedan.

Stock value is 225/50R18

Has anyone upgraded to 235 or 245 and if so, any feedback?

My apologies in advance if I was looking with my eyes closed.

 

I think you would be okay with 235 but you should drop to a 45 profile. I'm not sure what your ride height is, but my issue with this on my 09 X is if I go with a 235/45 R18 it will increase the already awful stock wheel gap. The rims are 18x8 so the 235 will definitely work, I would say 245 is gonna be a little wide for 8 inch wide rims I wouldn't go with 245 because the tires will bulge and just won't look good. what you want to keep in mind with switching tire size is the overall rolling diameter of the wheel you want to keep it as close to possible as the stock diameter which is like 26.8 inches I think. use a good tire calculator to determine how close you are to that diameter.

 

245/45R18 should fit and be very close in size to the OEM tires. They might be a bit wide for the rim though.

 

Okay so maybe I should have looked a little bit better at the tire calculator myself, I use Tire size calculator as a tire calculator. with a 225/50 18 the diameter is 26.9

235/50 18 is 27.3
235/45 18 is 26.3

245/50 18 is 27.6
245/45 18 is 26.7 this actually seems like the best fit and is the closest to the stock tire size the only reason I say this size will bulge a bit is because my brother used to have 245/45 tires on a 8 inch wide rim which is the size of our stock wheels and there was definitely a bulge at the bottom of the wheel, in my opinion it was an eye sore to look at and didn't think it was worth it increase the size of the tire. however, different tires have didn't sidewalls so that can play a factor as how this will actually look.

hope this helps

 

These are 245/50/zr17's on my 2009 G37x. General G-Max 03's

 

245/45-18 has always worked out well.