I have the 2011 F550 6.7, OEM rims and tires are 245/75/17. I plan on installing 285/70/17's on the same rims. For the moment, from just a visual, the 285s seem that they will fit without rubbing or touching. To be on the safe side, I will look into the spacer arena. Not sure what type bolt pattern or whatever. Im guessing 8x200. anyone have any experience on this?

 

If you tow or work your truck, you might want to stay away from spacers.