I want to put some KMC XD monsters on my F150 but I'm not sure whether to put 18s or 20s on. And I don't know what size tires would be bigger then the stock but not to big to where they would rub. Any advice?

 

does your truck have a level or is it stock? i prefer 18's, I. there cheaper & 2. if you do any off road driving, you.ll get more sidewall tire. Probably the most common size is 33 x 12.5 x 18 or 20. You might have to trim thew valence if you dont have a level otherwise with a level they work fine with no rubbing

 

I wouldn't go any smaller than 20s, But thats just me.. You would need to answer these 2 questions so we can point you in the right direction.
-Do you have 4wd
-Do you have stock suspension?
You will be able to fit 33x12.50 tires without any suspension mods, But you will need to be careful with what offset you choose.. +18 offset would be fine without any suspension mods, But you can go pretty close to 0 offset with a leveling kit..

I have currently have a stock suspension FX4 with 33x12.50x22 tires and +18 offset on the XDs without any rubbing at all.
I just ordered a 2.5" leveling kit and 22x9.5 BMF Novakanes with 0 offset, They will probably rub a little bit, But I will do some trimming to make them work.

 

My truck is stock and yes it is 4WD. And i went to Discount tire and they said the biggest tire i can go with is a
285/50R 116S XL B. And i was thinkin about goin with Nitto Terra Grappler AT tires. And yeah i was thinkin about going with 20s now cuz my stock wheels are 18s already and i want to go bigger

 

Novakanes with 0 offset, They will probably

 

I'd suggest adding a leveling kit and going with 305/55-20's (33x12.50) on a 9 inch wide wheel with 5 inches of backspacing.

 

I agree.. Thats a very popular set up around here and no rubbing issues.

 

A small leveling kit as was suggested and 33" tires would look great. I like the look of 18's with 33's...just the right ratio of rim and tire.