I have a X sedan and am wanting to do something like 265/35r18's all the way around. I like the track prepped look so thats why 18's rather than 19's/20's. Im just wondering if its possible or even 275's all around. The most I have seen in the front was 245 so far. Also Im guessing my rim size will probably be a 18x9.5 with an offset somewhere from +25-+30.

Any help would be appreciated.

 

265/35-18 is a good bit shorter than stock. 265/40 would be a better fit. If it were me, I'd go for a 9.5 +35mm or so with 275/40 all the way around. 275 will look nice and beefy on a 9.5. 10.5 +45 would work better if you don't want to look too beefy.

 

Ok cool ya I was just thinking about the height of it earlier. But ya if I can do 275's with no issues that would be awesome. But do you think they would stick out much? I would like to keep it lined up with the fender as much as posibble

 

With an X you have to be extra careful w/ tire sizing, there's been a few guys w/ issues over 80mph when their diameters are off more than 1% from stock diameter. This calculator is very useful, you can try different tire sizes and see how a certain offset will fit. With 18" rims the compatible sizes would be~245/45/18, 255/45/18(marginal), 265/40/18 (1.5% difference), 275/40/18, so the 245s and 275s are the most compatible. If you want 275s all around it's going to take some pretty conservative offsets, you should plug various offsets into the calculator just to see how far they'll extend in the fender. A 9.5 +35 should work in back but the front is a bit tricky. Are you going to be dropped?
Here's the calculator
https://www.myg37.com/forums/tire_rim_calculator.php

 

Ya I looked at the calculator and it was kinda confusing.... but if I do lower it it may be only an inch or 1.5", no more than that.... trying to stay functional. If I have to do a conservitive offset that would be fine Im not too worried about the look of the rim more the size of the tire.