Your rears are gonna be hella stretched with 285's on a 20X11 wheel lol. I'm running a 295/30/20 Michelin Pilot Super Sports on a 20X10.5 wheel, fits awesome. Then again it all depends on the tire, every manufacture will make their tires differently, some will have meaty sidewalls like the super sports or some will be narrower.
You'll be able to pull off the 295's on the 11 inch rear. You can put a 305 also but you'll have to lower the aspect ratio to a 25 (305/25/20) instead of 30. Same will apply for the front, instead of 255/35/20 it'll have to be like 265/30/20. The rolling diameter is going to change no matter what. Michelin makes the PS2 in this size.
I recommend just plugging sizes into the tire size calculator and looking at the changes in rolling diameter, etc then choose from there. Try to stay close to stock as much as you can but remember it's still going to change no matter what you do since the sizes of the actual wheels are different from stock. Post pictures after! What wheels are you trying to go with?
Tire Size Calculator - tire & wheel plus sizing
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