Although since it is a +12 you can do a 315/70/17

 

how much further would they stick out past the fender vs stock? is stock +35mm?

 

18's and 17's might be...I know that the 20's are a +44mm...6.14" backspace. Close enough. So a +12mm is a 5.5" backspace if it is a 9" wide rim. Therefore you would gain about .5" clearance (sticking farther out the fender). Then the stock tires are 10.8" wide (275). You go with a 12.5" tire and you will gain about 1" of tire each side of the rim.

So overall, you are looking at about 1.5" extra sticking out the fender over stock.

 

295/70/17 or 315/70/17 with minimal trimming.

 

So with the 315/70/17 i would def have to trim?

 

I have 17x8 with +25 offset which would be equivalent to +35 or so with nine inch wide wheel. I have no rubbing. The trim may be as small as the plastic lower bumper valance but may be more.

 

Well hopefully i wont have to trim but if i do then i do thanks guys for the help ill try to find some pics of guys running a +12 offset so i can get a better idea

 

This is what my truck looked like in April of this year. 20x9 with a 5.5" BS or +12mm offset. 295/65/20 (35.1 x 11.6) Nitto Trail Grapplers. They stuck out about .5"-1" from the fender. You will absolutely have to trim the lower valence with bigger tires. Its not a big deal though. Its easy and doesnt look like a hack job.

 

Or you could do like i plan... 285/65/18 trail graplers on a 18x9 with wheel spacers... The rims im getting are a 0 offset so thats 5 inch back space then ima put a 1.5 spacer to get the stance im after

 

Why don't you just go with a high negative offset?