do u guys think this is a safe setup?

18X8 ET20 225/45/18 front
18x9 ET20 245/45/18 rear

 

No, it is very dangerous.

 

how about ...
18X8 ET25 225/45/18 front
18x8.5 ET25 245/45/18 rear

 

I kid. Honestly, I believe 18 9.5 +15 all around with 265/35/18's would be a wicked set up, and still give no problems. The sizes you gave are extremely conservative. They are so far removed from dangerous, it's incredible.

 

Use a offset calculator to compare your current wheels to the new wheels. With the new dimensions, check the car with a tape. Do you clear the suspension, brakes calipers and fenders? Reference: http://www.1010tires.com/WheelOffsetCalculator.asp