Wondering what the biggest size tire is that I can put on my stock f 150 xlt with 17' rims

 

Probably 285/70x17 is the largest recommended for a 7 1/2" rim width. Anything larger will have a wider recommended rim width. If you have a 4x4, they should fit okay. 2wd, I don't know if they would have clearance problems.

I've been thinking about going to this size on my 02 4x4. I drive out on the beach a lot and now I have to let some air out of the stock 265/70x17 tires sometimes when the sand is really dry.

 

I prefer taller but narrow. I currently have the 255-80/17 and really like them on a set of Ford take off rims. They measure out to 33x10 if that helps.