6.9 with a turbo and big tires = power loss?

[Dubshot]

i got a 6.9 with a banks turbo and was thinking of going to 35's to 37's and was wondering if it will highly affect my power, towing, and gas mileage.. this is my first diesel so everything helps..

 

[Worstenemy453]

The biggest thing is gears, if you do the correct gear ratio to make up for the tires, you shouldnt have a problem.

 

[kas83]

MPG will suffer some, no matter what, and regardless of gear ratio. Higher rolling resistance of taller, heavier and usually wider tires equals more parasitic loss, using more power to keep them going. How much it will affect mpg is not certain, but you're not gonna stay the same.

 

[Dubshot]

I have not done the math to see what are you guys getting out of yer 6.9 and are you turbo/or not. I know the gearing always helps but thats expensive i want to be able to go play in the mud with this thing sometimes too.. I guess I could always swap the tires everytime but that gets old..

 

[MUDKICKR]

what is your factory gear ratio? if you have 4.10s factory then add 37s it will end up like you have 3.55s
37 divide 31 equals 1.193548387
the multiply that by 3.55 which equal 4.2370. which is close to the factory 4.10s.
now if your running a 3.55 gear ratio then you will be in a little trouble, your gear ratio will end up between 2.73 and 3.08

 

[6.9poweredscout]

got 4.10's and 37's and no turbo, mpg is good, power is good, i like it overall. but it's in a scout, you guys have at least 1000#'s on me! my 250 with 3.55's and 37's with no turbo wasn't bad at all either!

-Jon

 

[lotzagoodstuff]

+1 on the rolling resistance/rotating mass, as well as the rearend gear making a big difference. I think the biggest MPG difference comes from your right foot, and high RPMs.

I have 4.10s, and in my truck I haven't noticed that much negative difference with my 35s for power or mileage, and I actually like the fact that my engine sweet spot which was about 62 speedo MPH is now a couple MPH faster, which makes me feel like I'm not looking as slow as I used to on the freeway

All in all, taller tires look better but power and mileage will suffer a little.

 

[12clip]

Anyone have any insight on what amount of lift would be minimum and what offset of rims would be ideal for 37" on a '93?

 

[Clydesdale]

Shave or space bumper, find a leveling kit, 2' in nose essentially, and you will be fine.

I like the looks of a 12 wide tire on a stock rim.

 

[12clip]

Really? I thought I was looking at a minimum 4" lift and some minor fender trimming aside from shimming out the front bumper.
What is the minimum rim offset to help with keeping the front tires off of the leaf springs and improve turning radius?

 

[6.9poweredscout]

i trimmed 6" off the front bumper on my '92 250 and 37x12.50's cleared.

-Jon

 

[adrianspeeder]

Really? I thought I was looking at a minimum 4" lift and some minor fender trimming aside from shimming out the front bumper.

On a half ton yes.

Adrianspeeder