docwatson wrote:And just to be clear, some R51s (S models) came stock with a 245/75r16. So clearly Nissan thought a 245 tire was ok.
On this anecdotal evidence about the Tundra, did you use the same exact tire other than 70 vs 65? Tread pattern and sidewall ratings can change the characteristics of a how a tire rides (and weight) substantially.
To throw my two cents in, I went from a 225/75r15 to a 225/75r16 and didn't see any mileage drop on my Jeep Cherokee.
You're right, the S came with 245's. I personally wouldn't want that setup but I particularly care about handling because of the roads (and manner) I drive.
The Tundra had Cooper Discoverer ATR's for all three sets. I had to put tires on that truck every winter (was driving 25k-30k miles per year). It chewed up the OEM dunlops in 15k miles.
I had a Cherokee many years ago as well and it pretty much got horrible mpg no matter what so I can't imagine you'd see much of a change. Mine was geared fairly low and was just a 4-speed auto so it had a lot of rpms at highway speed. I recall 85mph was about all she had before things started to get ugly.
The Tundra and R51 (and most any newish car today) have pretty tall gearing and final drives so a bigger tire diameter will have a more dramatic impact. I drive the same route everyday so my mileage is very consistent.