I am just getting into four wheeling and off roading with a 2004 Jeep wrangler (stock) that I have.  I am considering putting bigger tires on it but I don't have the cash for a lift kit right now.  My question is what is the biggest tires you can stuff under a stock jeep without running into problems?  I have talked to quite a few people and everybody seems to have a different answer.  Would I need to change the gearing on it as well?  Any help anybody could provide is greatly appreciated.

since jeep suspensions have so mutch travel you are better off just getting stock size tires with a more agressive tread until you can afford a lift. then skys the limit.

Yanni

30x9.5x15 is the biggest tire you can run on a stock tj  

I own a 04 Tj thats completely stock with no lift and i am running 31x10.5x15 and i havent had any problems with rubbing or spacing issues. just make sure to get the right amount of backspacing with the rims or the tires will rub when you turn.  

it all has to do with your driving.  i have a 79 k10 that when i bought it has 2.5 inch lift and the tires never rubbed for the previous owner.  I know have the same 35" tires and make them rub with 6" of lift.  How and where do you play is the question.  If you go with the 31x10.5 do not twist it up.  beside if you have no money for a lift then you need to take it easy anyhow so you do not break stuff.  Just use it to get to where you want to go.  

One option would be a body lift so you could fit larger tires and they are not that expensive.