I just bought an 07 Crew cab 5.4L 4x4. It has the 255/70/17 General ameritracs on it. I do some towing of a racecar in the summer so I know I need at least a C rated tire to be safe. However, I'd also like to fill the fender well gap a bit too. I've narrowed it down to the Firestone Destination A/T for my driving patterns.

factory tires = 31" tall & 10" wide
6 ply 255/75/17 = 32" tall & 10" wide
6 ply 275/70/17 = 32.2" tall & 10.8" wide
10 ply 285/70/17 = 32.7" tall & 11.2" wide

To me the bigger tire would probably look better but how much rougher would it ride than the 6ply tires? Also, is there any difference in ride quality/traction/handling based on the different widths?

 

It would be little or no more harsh with the proper inflation. Just like having proper inflation of the LR C tires (40-45 depending upon the recommended by Ford of that years model), the LR E will need to be run at around 45 (if max pressure is 65) or 50 (if max pressure is 80). You will have a bit tougher time towing with the larger tires. It will work the engine and especially the trannie a bit harder.
What rear ratio do you have. 3.55 or 3.73. If going to the larger tire, I would at least have a 3.73.
As far as traction, the wider tires would do better on dry and wet roads, while the narrower would do better in snow.

 

Thanks for the reply and info! I have the 3.55's so it sounds like I should probably stick with the 255/75 or 275/70. I guess I'll go with whichever is cheaper and that'll probably be the 255/75's.

 

Oh, and when you say it will work the truck harder, do you mean based on the diamter ot tire weight?

factory = 37lbs
255/75 = 43lbs
275/70 = 48lbs
285/70 = 53lbs

The 255's only come with 13/32 tread depth whereas the other sizes come with 15/32nds. I guess I'm leaning toward the 275/70 at this point.

 

Based on the diameter, as you are raising the final drive ratio. Getting closer to the equivalent of a 3.31 rear, which lowers your tow capacity. 275/70R17 is what came on my truck with the 3.73. You might also want to get the computer reprogrammed for the new tire size. It may help with the shift points.

 

Thank you. Yes, I planned to get the speedometer corrected.

 

That size is one that the dealer can program in. If that size is not listed on there machine, the 275/65R18 is exactly the same diameter, so they can use that. That is what I did with my 07.