[TXiceman]

The larger diameter tire has a large circumference which means for each revolution of the wheel it will travel farther. The larger diameter tire is basically changing you final drive ratio to a lower numerically (higher) drive ratio and it is now geared for lower RPMs at the engine and better fuel economy. If you go to a larger diameter tire, yo need to change to a lower ratio (Higher numerical ratio).

If you had a original truck rear axle ratio of say 3.42, the larger diameter tires would go toward a 3.08 ratio.

This is why I tell people that are towing and RV to not bother putting on larger diameter tires. It may look "cool" or whatever, but it is not the thing to do to help towing performance.

Ken