I have a 1998 Ext Cab 4X4 that OEM tires are 255 70 R16, on stock rims...

I wanted to purchase BFGoodrich All Terrains (like the look and the long lasting)

The guy at the local tire dealer told me that I cant go up any sizes without my tire dragging on turns? Does this guy know his stuff? What size can I get?

 

hes full of SHlT. you can EASILY fit a 265/75R16 stock or a 285/75R16 with a little torsion bar cranking.

 

You can easily fit 285/75-16's (33x11.50) or 295/75-16's (34x12.00) using the oem wheels.

 

Lazy salesperson, want's to sell what he has instock...my guess. I just put some LT265/75/R16's onto the stock rims for my 99F150 4x4. I cranked the torsion bars with Wandell's advice, strictly to level out the truck... I think it looks better!

 

You have tons of options and a few have been stated already. Sounds like the sales guy only wants to sell the stuff he has in stock!!!