The 315's are two inches taller. Other than that there is almost no difference in width. With proper offset either of these ties will fit fine. They are off road tires. You will lose mileage. You have to pay for your lifestyle. Have fun.

 

The difference in width will be 10mm. I know mm are a strange concept for you yanks so I'll convert it for you.

roughly 13/32 of an inch.

It will be 2 inches taller due to the increase in aspect ratio you put down.

Worse MPG on the taller tire. Both will look beefy on a 9" rim.

For reference I had 33x12.5 on a 9" Rim (About 315mm). Looked awesome.

I have 285/65/r18 KO2's on the same rim which is about an inch narrower. Doesn't look quite as beefy but still sticks over the rim a little. You'll like the tires.

 

Thanks kelaog. I originally planned on going with 285 but I already have 275 so it wouldn't be much of an upgrade. 305 measures 32.7" so again I'm only adding about 3/4" in height which isn't that impressive either.

 

Something that I rarely here anyone say about going with 315's or 35's is that, assuming you are going to actually use the truck off-road, you cannot fit a full sized spare in the factory location. I was set on 35's or 315's after the lift and considered how I would have to wag around a massive spare in the bed. Considering my bed is typically full of firewood, camping gear and dogs, it would really be a pain.

I am running 305's that measure a hair over 33" and have a full diameter spare. In the stock location, I can't even get a pinky finger between it and various metal bits but it fits and I am happy with that.

Do you really need a full sized spare? Yes. I tore a tire up about 15 miles away from pavement in the mountains and without a full sized spare, I was walking out. My freaking stock spare was a temp. donut!

 

Just did a 2" lift and I'm switching my 20"s for 305/65/17 Ko2s... i don't plan on lifting the back and i do pull a 7000lbs trailer on weekends so I'm trying to keep the tires inside the fenders as much as possible but still fill it out. Plus I do drive the sh*t out of it so i really do need room for the tires/suspension to compress. Ill post some pics when i get the wheels/tires on there.. Going with Method Standards 17x8.5 0mm