what size rims???

I am trying to find out what size rims I can put on my truck. I have a 2003 4x4 dodge quad cab with stock 20" rims. What is the smallest rim I can go with. I have been told I could go to a 16 but I was not sure. I would like to see about maybe a 16.5?? If anyone knows please let me know, Thanks

The smallest that will typically clear the brakes would be a 17" with a 245/70-17 tire size. We have not seen any 16" that will clear the front calipers.