I needed to trim my front bumper on my 2000 Grand Cherokee Laredo because I am running 245/75R 17. There was a very small rub on the inner fender well mud guard.
I cut about 1" off the bottom bumper and tapered it towards the middle. Then I cut the mud guard about 2 1/2" from the bottom with a curve towards the middle. That didn't work--still rubbed. The bumper was fine--plenty of clearance.
So then I cut the mud guard straight across to the sway bar. This exposed the fog lamps, but I think they will be ok.
I'm running a Skyjacker 2" BB and have the Up Country suspension package. I have 20" in front and 21" in the rear.
Here are the pics of the final cuts.