Hello

I have a question about rubbing with not rolled fender.

If 275/40/18 +20 offset does not rub on stock height and none rolled fender,

295/35/18 +30 offset would not rub neither?

because those +20mm in tire width will be added as 10mm to each side of wheels so

+10mm in offset will counter increase of width of one side.

Am I right? or am I making mistake?

Thanks!

 

the +20 "sticks" out more than the +30 does

 

In theory, you are correct. But NOT every tire is made the same. Some have square sidewalls and some have round sidewalls. If you stick withe the same brand/model tire, then it should fit fine.
-GP-