Originally Posted by TheDon
Thanks Raynval, I do pull a trailer sometimes right at 10K in weight but maybe once every month so its not a big issue. I heard that, and reading from the chart that once on the highway the mileage gets better with bigger tires? when looking at the chart and driving at lets say 65mph, tires that are smaller run a higher RPM and the bigger the tire the less RPM's. Its only in the stop and go situations that seem to effect mileage, would you agree?
Well it's hard to say about the RPMs, with the taller ratio (taller tires) there's more load (less mechanical advantage, gears are spread further apart, and the larger tires cause more drag) and the truck will drop a gear quicker (higher RPMs) and more often to try to overcome that load (or you have to apply more throttle which really sucks the gas). So, it really depends on the exact load and speed your going. But, I'd say that 35" tires are not going to get better MPG than the stock tires on the Highway, or in any condition I can think of, except for mud, where the stock tires are just spinning and your not going anywhere. Then they will really get better MPG!!
If your concerned about MPG, you probably want to stay with a A/T over a M/T, and might want to consider something narrower with a smaller contact patch, like a 285/75/17. Here's the best article I could find, keep in mind it compares a road tire with a A/T, it's even a lot worse with a high flotation tire.
I still think your gearing and 35" tires would work fine, although if your trailer is really that heavy, I'd be a little concerned, thats a lot of trailer for a gas motor. Do you have to pull it far? I pulled my Toyhauler the first time this weekend about 300 miles. I'm guessing my Toyhauler as loaded this weekend is around 5K pounds (smaller Toyhauler, no bedroom about 24'). It pulled fine, no problems. My computer said I was getting about 6.5 MPG, I hoped it would be better when I manually tested it. It wasn't, almost the exact same, 33.5 gallons for 220 corrected miles, or 6.57 mpg. 90% highway between 65-75 MPH (I need to slow down and get a little better MPG). Thats going to make for a tuff racing season this year.