bigger tires on stock rims

i have thirties on the stock tacoma rims right now...
can i go any bigger without it causing any problems...
31's?...32's?...

You can go much taller, just not much wider. You can run a 33x10.5 or 32X11.5. I think Interco also makes a 32X10.5. I assume you are running a 15X6 rim. All of these will work but even on a seven inch rim you are pretty much limited to 11.5" wide tire.

I'd go no bigger than a 32. You may get some fender scrub at full steer and full bump (i.e. turning hard into a dip). For regular driving, it would be fine. I wouldn't recommend going to 33's without a lift.