Well, that will depend on the backspacing of your new wheels. My 285/60/R18's on STOCK wheels are dead even with the factory fender flares. 305's on the stock wheels would stick out a little less than 1/2" (20mm=0.8"), so .4" per side of the wheel. Choose the tire width you want (and how far you want it to stick out), then choose the wheel backspacing.

 

Thanks Sooner! You've been a big help. I think I'm leaning towards the 305s. I want to do the 2" level so I think the 305s will fill the wells a little better!

 

https://www.f150online.com/forums/me...termarket.html

there is a 12.5 inch wide tire (305) on the 20 inch monster. i have the 275 (11 inch), so the tires in the link stick out about 3/4 of an inch more than mine do.

 

Thanks jdeacon, that definitely helps!!

 

Help me out!! Is that the offset? I don't know if I like how far the 305 sticks out. What should I be looking at to have the tire flush/even with the fender?

 

my 275s on the exact same wheel you are looking at are 100% flush with the fender. in the link above the guy is running the exact same wheel with a 305 tire, so his stick outside of the fender around 3/4 of an inch. if you want pictures i can take some of my set up tomorrow. but i can tell you based off of my own truck, 275s will be flush and 305s will stick out

 

Awesome!!! Thanks again! Both tires are almost the same height correct? Basically a 33" tire? So I'm really looking at width between the 305/55/20 and 275/60/20?

 

100% correct

 

Thanks for all the help guys!! I just went to my local discount tire and they beat the online price I found. I went with the Monsters and the 275/60/20s. $1,775 out the door. I think thats a fairly good deal. I've always had a good experience with Discount!

 

I'm looking at doing the same wheels and tires! How do you like them and can you post some pics?

 

Any of those eBay links lying around possibly?

 

I was prepared to use this one but Discount tires didn't want any proof. I just told them the price and they beat it. Looking back I could have told them less!! I will try to post some pics a litle later today.

http://www.ebay.com/itm/20-XD-MONSTE...91d69c&vxp=mtr

 

I absolutely love them! I'm amazed at the difference they make. I did the 2" level also but you don't have to. They fit under the stock truck. I'll try to post some pics but Flikr hasn't been cooperating for some reason.

 

http://www.flickr.com/photos/92244255@N03/8484603240/http://www.flickr.com/photos/92244255@N03/8484603240/ by http://www.flickr.com/people/92244255@N03/, on Flickr
http://www.flickr.com/photos/92244255@N03/8468900146/http://www.flickr.com/photos/92244255@N03/8468900146/ by http://www.flickr.com/people/92244255@N03/, on Flickr
http://www.flickr.com/photos/92244255@N03/8440526753/http://www.flickr.com/photos/92244255@N03/8440526753/ by http://www.flickr.com/people/92244255@N03/, on Flickr
This was a poor attempt at before/after
Before.....
http://www.flickr.com/photos/92244255@N03/8441626316/http://www.flickr.com/photos/92244255@N03/8441626316/ by http://www.flickr.com/people/92244255@N03/, on Flickr
After......
http://www.flickr.com/photos/92244255@N03/8440534009/http://www.flickr.com/photos/92244255@N03/8440534009/ by http://www.flickr.com/people/92244255@N03/, on Flickr

 

Looks good. I like that wheel and tire combo on your truck!