I have an 09 X and wondering if I can squeeze 255/45-17's on it. What's the largest size tire anyone has been able to get under there X without replacing the rims?

 

Ill with 235/50 just to be on safe side.

 

I don't see an issue with clearance given it's not a whole lot wider and I'm guessing you aren't dropped. Only recommendation is to keep the rolling diameter as close to what you currently have. So if that's a 225/55 like I think sedans are, I'd say go with a 255/50 as it'll get you closer.

 

A buddy of mine is closing down his dealership and has a bunch of primacy mxv4 in 255/45-17 and I can buy them for 30 cents on the dollar. And Knowing that in 20K, Ill be replacing the Eagle GT's which are on it now. If they will fit I certainly can't pass this deal up.

 

Ah... Well as far as them physically fitting I see no issue. Worth waiting around for more opinions, you post this in the Sedan section too? You'll probably get more visibility there.

 

Just be sure to use this calculator w/ your old and new tire sizes. keep the new diameter within 3% +/- of your old tire's diameter and you'll be OK. obviously as close to 0 is your goal. 255s should fly, might get a bit more center tread wear but other than that should be fine.
https://www.myg37.com/forums/tire_rim_calculator.php

 

See my thread in my signature.

 

If a sedan, we show 245/50-17.

 

Yes, its a G37 X sedan. Concerned about potholes and such..