A couple questions.

Which is better for off roading?

Are the stock tires they give you with the 20" wheels wider? if so by about how much?

Will the truck be taller? if so by about how much?

 

truck will not be higher. that depends on the tire diameter.

Which is better for offroading? that is a broad questoin. It really depends on what you want to do. 20" rims will help you keep your bead seated better, but 18" will give you a little bit better sidewall flex. Either way, there isnt enough difference between 18" and 20" rims to matter. Then it boils down to what tire and what size tire do you want to run? in reality, 17" rims are probably better bc they are becoming a lot more popular in the offroad world. replacing the crappy 16.5 cwoozy rims...

 

Only metric tire sizes go up with rim size such as 365, but standard like 31s or 36s stay the same.
I would say the smaller size rim cause tires will alot cheaper and the smaller the rim the less damage can be done to it.

 

anything bigger than a 16" rim doesn't belong on a pickup.

 

unless you absolutely have to... like on michelin XL's... no other option. agreed, it would be better not to...

 

ok let me rephrase that unless your running semi tires or ag tires no rims over 16" belong on a pickup

 

There aren't very many off-road tires over for 18" or 20" wheels, but 17" is starting to pick up. Selection may be better in a few years, though. I wanted to get 17" or 18" wheels and tires, but couldn't find a tire I liked, so got 16" wheels and tires instead. (I had 15" before) Of two tires with equal diameter, the one with a bigger wheel will often balance better, and this is one legitimate reason to get bigger wheels. Alas, most of the tires for them have very low ratios, so they only good in a mall krawler.

 

i would stay away from anything bigger than 17", unless your running military or ag tires

 

not to mention 17, 18, and 20's are more expensive than their 15, 16" counterparts!

-cutts-

 

The bad thing is, you can't run a rim smaller than 17 on the new F-150 FX4s.
I like my 15s, tires are ALOT cheaper than 18 or 20s.

 

But if you want D or E rated tires, finding one for a 15" wheel may be a bit (?!) difficult. That was one of the reason I went to 16".

 

I personally step down from my factory 17" wheels to 16" wheels on all my new fords once the 17" tires are wore out. Anything bigger than 16" is GHEY and should have never been put on a truck like monsterbaby has already said!

 

Amen brother

 

The 20" tires on the new F150 Fx4 are P275/55R20 Pirelli Scorpion, the 18" are either LT275/65R18 LRC Goodyear Wrangler AT/S or P275/65R18 BFG Rugged Trail TA.

They all have the same section width. The Goodyear AT/S has the most agressive tread pattern out of the 3. The BFG will probably wear the best. Don't know much about the Pirelli performance. The 20" package will be more prone to rim / tire damage off road due to the smaller sidewall height.

Pirelli 20" diameter is approx. 31.89 in
Goodyear and BFG 18" diameter is approx. 32.09

 

Due to the brakes, that may not be particularly easy to accomplish on some newer models.

I don't se why a 17" or 18" wheel would be GHEY, just put on a reasonable tire and. Now, people having ta couple of inches of tire that's barely bigger than the wheel, that's a different ballgame.