The diameter is identical 728 mm , the tyre is the right width at 245 ( 9 inch approx ) , 275 is too wide , !! ( 11 inches approx )Bit narrower, similar diameter.
Mine is on 265/40/20 but tempted to try 245/45.
265 40 20 is a size often used on staggered wheels when the suppliers cant be arsed to stagger the tyres as well , 245 45 20 feels so much nicer on the steering , every one who listens to this advice comments on the improvement . Note that running different diameter tyres front to back isnt a major issue unless you have a 4 motion then its critical to get right .