On my 05, I want to get my RPMs to somewhere around 1800 or 1900 at 70MPH. It is an 05 dually 4x4 quad cab with the new six speed, so it is geared pretty low. I am at 2200 to 2300 at 70MPH. I want to go to a 35" Nitto Mud Grappler. Is anyone running this combo? Has it made a mileage increase? Power increase at 70MPH due to the peak torque is at 2000 RPM?
Or would anyone know a formula for finding out the difference in tire sizes to my RPM @ 70?

 

Not having your tire combo, but you should see a mileage drop when going to 35's. The extra weight and rolling resistence will more than offset any expected increase in mileage.

Nav

 

You'll lose power going to the larger tire.

Here's the formula:

Current RPM @ given speed X (new tire rpm/old tire rpm)= NEW RPM.


In English (since that is a lame explanation), you'll need to find the "revs per mile" for your current tires and for any tires you are proposing to install. Typical stock tires are in the 650 revs/mile range. A 35" tire will be around 600 revs/mile, give or take.

So, take your NEW tires spec (600revs) divided by the original tire spec (650 revs) to get something like 0.92. Then, you will multilply your original RPM times this factor to find the new RPM.

So if you have 2300rpm at 70mph, your new rpm is (2300*.92)= 2116 RPM.


35" tires on a dually are a pain. A 235/80R17 is about as good as it gets, yet you are still geared too low.

Sounds like you may have the "wrong tool for the job" if you want a shorter geared plaything (726hp in your sig). A dually with the G56 is a workhorse, no a playhorse.

Good luck.

Justin

 

SOME people have noted mileage gains going to a 35 tire, but they are slight, and always happen with mild tread.

99% of those who install larger tires will NOT see better mpg, though it's more likely with a 33" tire and hwy tread (like a Michelin M/S) than any other, imo...


jh

 

Unless your truck is going 70mph when you climb in the door, don't expect anything but a moderate decrease in mileage!