what is the biggest tire i can put on an 07 fx4 with no leveling kit?

 

Using the oem wheels, a 33x12.50.

 

thanks, what if i went with a 22" rim?

 

It will depend on the wheel. I have 305/45-22 tires on 22x9.5 inch wheels (with 6.7 inches of backspacing) on my Expy. They are basically a 33x12.50-22 tire. If you go with that size, I'd suggest installing a set of lowering shackles or removing the oem lift blocks to lower the rear 2 inches.