I have 275/65/18 KO2's on standard rims. I still have my mud flaps on and have no rubbing or scraping anywhere....but I did have to work a bit to achieve this.
Not that it makes much difference but I do have Fox coil overs with around 50mm of lift.
When I first put the tyres on, they rubbed on the mud flaps and also on the plastic inner guards. We then did an alignment and adjusted the castor which effectively moves the wheels forward and stops them rubbing on the mud flaps /inner guards. So all good, except the tyres then rubbed on the underside of the upper control arms instead.
So I then swapped out the upper control arms for some with a bit more delta between the arm itself and the ball joint. This stopped the tyres rubbing on the arms. The upshot of all this is that 275/65/18 tyres will fit but you will need to do an alignment and set the castor as far forward as you can go (To still stay within the spec that is!!!) then you either need to modify/remove the mud flaps OR change the upper control arms if you dont want any rubbing.
I'm super happy with the result.
Cheers