Size of tire in order to tuck???

Hey everyone,

I need to get a tire that will not expand further than my rim.

Right now it rubs like crazy and they wont tuck up in the fenders. What I have is an 2010 Escalade 18"x 8" currently sitting on P245/50R18.
Please help me figure this out. thanks in advance

i have the same rims but in the greyish color
im running 225/40/18's
my rear tires are all but tucking in back and they only rub when truck bounces a good bit, have to hit a big bump or turn sharp at a high speed to rub in front

215/35/18 is what I ran on my Navigator wheels and QX56 wheels with no rubbing at all.