[fourtailpipes]

one problem with 275s is the diameter. you'd want a 275/30-18, but that's a nonexistant size. only 275/35-18 is available, which is too tall. the gearing is already long in this car, and a 4.3% increase in the diameter of the driven wheels further lengthens the gearing and equates to a 4.3% reduction in torque application, or approximately 12.9 ft-lbs in any given gear at any given speed. to make up for this you'll occasionally have to downshift earlier/more than before. this could of course all be fixed with an adjustment of final drive ratio. or you could get the offset JUST right, and use a 285/30-18, which is a somewhat common size, and has a diameter pretty close to the oem tires.

edit: none of the above would be possible on stock wheels.