I have an 09 F150 FX4 with an AS 2.5" kit on....im looking at getting the Ballistic Jester wheels in either 18" or 20". The offset and backspacing options are:
1.) Offset: +12 Back space: 5.47
2.) Offset: -12 Back space: 4.53

I think #1 is the correct one but im not sure, which one should i go with???

The tire choices i have come to are either the Procomp Xtreme AT's or the BFG AT's. I know the price difference between a 18" tire and 20" tire is pretty big. The sizes are 305/55/20 & 305/65/18. My question regarding tires is, what is the difference in sidewall height between the two tires? How much more side wall will i have on the 18" tires vs the 20" tire?

 

33.2x12x20 and 33.6x12x18. Give or take a little because brands vary a little in their actual sizes...It should be about 1.2" difference in sidewall. I think the tire choice for the 18 might be a little tight if you choose to go with the negative offset wheel. Im sure you can make it work with some light trim work,but i do know with my 305/55/20's i had to trim some with the -12 offset. It wasnt a big deal though. The 305/6518 is around a half inch bigger then the 20"tire. Hopefully that helps and im sure someone will get you straightened out of I have my figures messed up. You can also search those manufacturer websites and they usually have there specs on the tire sizes.

 

What is the width of the wheels? You are basically comparing a 33x12.50-20 tire with a 34x12.50-18.

 

18x9 and 20x9 are the width of the wheels

 

Here is a link to a tire calculator - it will get you close based on the tire specs you input. As mentioned earlier here - you will have to go to the manufacturer's specs to get even more dimensional detail - good luck -

 

I'd go with the version with 5.47 inches of bs. That wheel will stick out about 1.5 inches farther than the OEM wheels. The version with 4.5 will stick out about 2.5 inches farther than the OEM wheels.

 

you forgot the link!!!!