what's the biggest offset we can get
 

i think we have 42 offset??? how big can we go before we start rubbing on the outside. assume that the overall wheel dimensions are very close to stock, regardless of rim size or tire aspect ratio.

45 offset is as high as you want to go.

Lower offset will move the edge of the rim farther out, as will rims that are wider than stock 7" wide. Stock 17x7 rims are 45 offset.
Higher offset will move the inside edge of the rim closer to the suspension components.

oh. i guess i had it backwards...

in that case, what's the lowest offset we can run with no rubbing??

stock is 45, you could run a 0, that would push the wheel way outside the fender, no inner fender rubbing...I think what you mean to ask is what the offset that pushs it out to the fender and not beond without killing the fender...

That would be around 35.