20's = too big. period.
19's = pushing it. your gonna have to have proper fittament/look to pull this off
18's = will look very good, i feel that 18's fit the wheel well very well on our cars.
Are you going for this look? BTW these are 22's and 20's will look much the same....TERRIBLE. There are FEW FEW cars that actually look good lowered with 20's.