hey. new to the forum thing and i've never lifted my own truck before. i was curious if i lift it do i need to go with a wider wheel or can i use some sort of spacer. which one is going to effect my gas mileage the most. it has 20x9's already and will most like;y stay with a 20 inch wheel. probably do about a 6"lift w/35's or so. i have an 07 dodge 1500 hemi.

 

Welcome to the site. I will move this thread to the third generation Ram section and you may want to check their FAQ,
FF

 

6" and 35s is about as big as I'd go with an IFS truck. The 20s are heavy though and will put a little more stress on the front end and cost you a bit more gas than a smaller wheel.

The biggest problem you are going to face with an '06+ Ram 1500 is that unlike the '02-'05s which had a torsion bar front, you have coil overs which yield less room for tires. 35x12.5s are going to be close, might not quite make it with the stock wheels which don't offer too favorable backspacing for wide tires. Might need a small spacer with the stockers. If going to an aftermarket wheel, something with about 4.25-4.5" of backspacing and a negative offset should clear 12.5" wide tires without the need for a spacer.
If it were me and I was going to have to get new wheels anyway, I'd be looking at 17s, especially if this is a 4x4 where you want all the sidewall you can get for off-road. Benefits to a smaller wheel would be better gas mileage, higher towing capacity, more sidewall, WAY cheaper than 20s and a 35x12.5x17 tire will be much cheaper than a 35x12.5x20. The only thing you really lose is the "bling" factor that big, honkin' wheels give you...

 

Nice write up Hammer.

Also, check the Wheel fitment guide as it may help too.
https://dodgeforum.com/forum/3rd-gen...dodge-ram.html