Hi , I was wondering what is the biggest tire size i can run on a 1999 Ford ranger Xlt 4X4 without and rubbing. im running p235/75r15 right now but have lots of space. Also is there anyway i can lift the truck in a cheap or free way to make the most space possible? thanks.

 

31's will fit just fine without a lift. Cheapest "lift" will be cranking the torsion bars. But actual lift that will make the truck taller for bigger tires is going to be a 3" block lift. See attached hyperlink for in depth explanation.
Chart of maximum tire size - Ranger-Forums - The Ultimate Ford Ranger Resource