I've searched and searched, but haven't found anyone with a problem quite like mine.

Truck: 04 Supercrew 2WD
Lift: 6" Fabtech
Wheels/Tires: 20x10 Moto Metal 951 4.79BS / 35x12.5/20 Nitto Terra Grappler All Terrain

The wheels and tires are brand new. They are rubbing the bottom edge of the front bumper. I trimmed the lower valence back, only to find that the tires were not only hitting the valence, but the corner of the bumper itself. I've double checked all of the specs on the wheel and tire setup and it's legit, I know I've got the right parts.

Anybody have any suggestions on how to alleviate this?

Thanks in advance.

 

your wheel specs are what is causing the rubbing most likely. so its hitting the metal part of the bumper? why not get a 2" spacer or bilsteins if you already have a spacer and get a couple more inches and that should solve your rubbing issue

i have a 6" lift wheel specs are 4 5/8 i think and 9" wide and im 4x4 so 2" higher than you and i occasionally rub if im on a hill or going over a bump

 

add more lift, get some spacers for the top, unless you got coilovers, then crank 'em

 

Wheel's are out about 3 1/4 inches more than stock, maybe if they were tucked in a little more they won't rub. What's the recommended wheel size for your lift?

 

Like they said, the wide wheel with a shallow backspacing is causing your rubbing. You could add a little more lift or change wheels. You may be able to space the front bumper out some, but that depends on how the bumper mounts. I know on 99-07 SD's, a lot a people were able to stack some washers between the bumper and the frame to space the bumper forward slightly. I don't know if this will work on your truck however.
You can always trim the bumper slightly. You can put tape on the bumper, mark a line and carefully trim it with a sawsall or cutoff wheel. You will want to cover the cut with some clear paint to prevent rust if you have to do this.

 

20x10 4.79BS
There's your problem.