I am thinking about changing tire size on my 2007 F-150 2wd. Has anyone done this?

My truck currently has P235-70-17's on it, and I want to step up the size a little to LT255-70-17's. I believe this is the stock tire size on the 4x4's. Has anyone changed out their smaller tires to a larger size? From my conversion chart I think it will be about 1 inch taller than the old ones. How much will this affect my speedo? I don't want to have to flash the computer just to change tire height, but I would like something to fill up the wheel well a little more. I am also going to get something with a fairly aggressive tread pattern because the OEM tires suck badly. 15000 miles and they are very worn. I don't drive the truck hard either. Main question is do you think it will mess up the speedometer and odometer too badly, and if so can I go to a 255-65-17 that will be roughly the same height, and be ok?I am thinking about changing tire size on my 2007 F-150 2wd. Has anyone done this?The link is a conversion calculator which will tell you the effect of the change on the speedometer and odometer. Going up to 255 will change things less than 5% which is nothing to be concerned about. In fact most stock speedometers are calibrated about 5% too fast. It's very likely the change will make things more accurate. Run a measured mile on the interstate or better yet 10 miles using the mileposts and see how accurate your speedometer and odometer are now.