I have an 03 disco with a terrafirma bumper and winch. Currently running 255-60-r18's.

I am considering doing a medium duty OME suspension and I was wondering if I will be able to run 265-70r18's. I really like general grabber tires and they are affordable in that size.

What are these upgrades going to do to my mileage?

 

Also: If I just leave the tires I have on now will it look funny with the OME med. kit?

Would it be ok to just do shocks and not new springs at the moment? Im at 150k

 

You will wear out your new shocks prematurely if you don't upgrade the springs.

Consider that the springs are probably a good 1.5 shorter due to sag. Your new shocks will feel good for a while but will take the full weight of the truck with worn springs.

Then when you buy new springs and raise it up 2 inches, the shocks will be stretched out and also operating 2 inches less compressed.

Just do it all at once, I waisted a set of Bilsteins in six months this way.

 

I have 255/60-18's on my 01 now and I can't imagine running 265-70-18's unless I would re-gear to 4:11's at the same time. That would be about a 32.5" tall tire.