i have a 91 sidekick with a 1.5 inch lift. ive been looking for wheels and i wanted to know, whats the widest set of rims i can put on it.

That greatly depends on how you feel about sheet metal trimming... If you go much wider than stock (in backspacing or width) you will start to fender rub durning compression when turning. If you dont mind taking a sawsall to your rig, I have ran as wide as 10" rims (15x10 w/ 4"bs). But it required adjustment of the steering stops and some fender trimming.

Zig