rim size and lowering
 

i'm wondering if I can run 17x7.5 rims with lowering 3 inches.. i'm lowered an 1.5 inches right now and running stock rims and tires.
i'm just wondering if i can run that or not.

You'll need camber plates to fix the horrible negative camber that will be introduced, and you may run into issues with the tire occasionally contacting the front and rear of the wheel well, but it should work.

I'm struggling to understand why you'd do this anyway. With a 3" drop, the car will be undrivable and handle poorly.

Rim size AND rim offset would come into play, but just about anything is going to rub with the car lowered that much.

And your real problem will come from speed bumps and any driveway with more than a 1% grade.

you can also have the fenders roll/pulled if you experience rubbing.

but like stated above, handling will be poor. It is probable that your geometry will be compromised and travel will be almost non-existent.