I have seen 31 x 10.50's on stock rims (15 x 5.5) but it didn't look safe to me. I ran 235/75's on stock rims with no problems. A friend of mine ran 30 x 9.50's on stock rims for a couple of years with no problems.
I know a guy that ran 31x10.5's and dropped them to 5psi when wheeling. Worked fine. The problem you will have, especially if you get any kind of aggressive tread, is the tires will rub the springs when you turn. I run 31x10.5 mud's on 15x7's and have no rubbing. HTH.
I just installed a set of roadmaster 30 X 9.5s on my Zuk with a calmini 2" reversal lift & doetsh shocks on stock white wagon wheel rims..... NO RUBBING ANYWHERE.
oldfartzuk on South Carolina coast....