I took a guess at your new tire size, but this looks pretty good to me: THIS IS BASED on the info you provided - stock off set of 55mm. This info is not verified.
WHEEL FITMENT, TYRE STRETCH, ROLLING RADIUS AND SPEEDOMETER ERROR CALCULATOR
Insert your existing wheel and tyre specs, and the desired size, and the outcome is shown on the diagram. Bear in mind most tyre manufacturers vary slighty from the specs, and that it could be dangerous to run tyres on wheels they aren't designed to fit. The strut shown in the diagram is for show only - Don't worry if the wheel looks like it fouls!
TIRE WHEEL
Width Aspect Diameter Width Offset
Existing 245 45 18 8.0 55
New 275 35 19 10 55

Old New
Diameter 677.7mm 675.1mm
Circumference 2129.1mm 2120.9mm
Poke 46.6mm 72mm
Inset 156.6mm 182mm
Speedo error 0% 0.39%
Reading at 30mph 30mph 30.12mph
Reading at 60mph 60mph 60.23mph
Ride height gain 0mm -1.3mm
Arch gap loss 0mm -1.3mm
Going to inset 25.4mm (1") more than stock, and stick out or "poke" 25.4mm (1") more than stock. I don't know if that's acceptable? Anyone?
EDITED: Stock wheels are 8" width, not the 8.5 I had in there originally. Please review all numbers as they have changed. I have adjusted everything to be in line with the new (corrected) specs.
GJ