i just recentlly bought an 06 FX4 4x4 and i was going to get the 20" rims and perelli tires from ford and decided against it and i am going to go after market. if i put 20" in place of the stock 18" will it fit right and will there be any other problems i don;t know about??

 

You should be fine, as long as you find a rim with the right backspacing. The wheel manufactures seem to do a better job on this with 20 inch and larger wheels than on 17's and 18's. A set of 305/55-20 (33x12.50) Nitto Terra Grapplers or Toyo Open Country AT's would look great.

 

I have an 06 FX4 with the 20,s, I believe they are 275/55/20 Pirelli Spiders and just had them mounted on American Eagle 20's. Look great, no problems...But, how big a tire can you go on the 20's without having to raise the front or cut any trim pieces.