seadoons

I recently put 285/65/20 BFG ATs on my truck. The stock tires were 31.9 inches tall; these are 34.6 inches. The stock tires were 10.8" wide; these are 11.2" wide. These are also load range E / 10 ply tires.

The truck definitely feels more sluggish as i am running 3.55 gears in the rear and the 5.4 V8. My gas mileage seems to also really have taken a hit.

I have a few days left to return the tires for something else.

What causes the drop in gas mileage? The additional height? The additional width?

Would a tuner help make the truck feel less sluggish and get me back that gas mileage that I lost?

Most tires that i see that are a bit smaller, like 305/55 and 275/65 are all load range E tires. I am considering going down to a 275/60 Cooper that is a P tire (not LT) and is something less that load range E.

Thoughts?

djfllmn

iTrader: (1)

increased weight

height

width

NASSTY

Yes, yes and yes.

sgtpatiolantern

Yupper. All of the above. Also tread. More aggressive treads tend to cause more rolling resistance.

djfllmn

iTrader: (1)

you also have to use a little more brake pressure to stop larger tires....a lot of people dont realize that the heavier you brake your gas mileage takes a little hit

MR.FX4

Tuner will help, but probably won't get back to stock as far as mpg

JLonsinger2011

getsomegurrrrs

deedlebag

The tuner will help, at least for me it did greatly. MPGs went up slightly, but the biggest thing was when I put the 34s on mine, I could just "feel" the extra weight of the tires, with the tune it feels like I am running with the stock pirelli's again.

truckwheelin

Not calibrating will cause the computer to calculate your MPGs lower than what they should be. Distance covered / fuel used = your MPGs. Your fuel use will go up because of reasons mentioned above (mostly mass and resistance), but the distance covered remains the same if not calibrated. Your computer calculated MPG is therefore lower than it should be. Once you calibrate, your distance covered will increase, so the MPG loss should not be as bad as previously reported.

On the note of mass: choose the lowest weight tire and wheel combination if MPG is your main concern with upgrading your tires and go with a shorter tire, or regear. Some examples... Toyo's and Nitto's are known for being heavy. The BFG AT KO's are actually mid range weight for Load E's. All of these will be heavier than any non-LT tire. The taller the tire, the further away the mass is from the axle and the more work your engine has to do. If you want tall tires and want to adjust the work load, then you will want to regear.

seadoons

I can definitely "feel" the weight of the tires now. I guess the real reason for my question is I am considering swapping down to a smaller tire but am not sure it would be worth it.