Fuel Economy Blows: Takin Lift Down and Moving to smaller tires: Question(s)

[Earl H]

I just purchased a 2004 Excursion Limited. Its a Southern Car and is in excellent shape with relatively low miles @ 84K. I bought the vehicle for Wife to use as her DD. We needed something big and go Diesel for the F/E seemed to be the way to go. The vehicle currently has an 8" Superlift Kit with 37" Tires. The truck looks great and we love it (after many Suburbans/Yukons), however the "problem" is my F/E blows. I got 15mpg on the 700mile trip from GA to MI. City is just above single digits. I'm not sure if we'll even get 400 miles out of the 44 gallon tank in combined driving.

I am in the process of selling the lift kit and tires. I am planning on lowering it to stock or close to stock (2in.) and going with 18" wheels and 33" tires.

Questions: what is the widest tire that I can put on with the truck at stock height, without rubbing. I am considering the following tires: 325/60/18, 305/60/18 and 295/65/18: all are about 32.5-33.4" tall.

Anyone with estimates on how much F/E will improve with the tire change? Lowering? Will the 325 width yield much different fuel economy than the 295?

If you've done this or know of someone who has done this, please post your results.

Next step: tuner for F/E improvement.

Thanks in advance.

[SickStroke6.0]

I have 325/60/18's. They rubbed a tiny bit at full lock, but I trimmed the lower valance on the bumper and zip tied the fender wells back (I used super thick zip ties ) and now it does not rub at all

[Earl H]

Originally Posted by MacbooknMyTruck

I have 325/60/18's. They rubbed a tiny bit at full lock, but I trimmed the lower valance on the bumper and zip tied the fender wells back (I used super thick zip ties ) and now it does not rub at all

Any change in F/E (vs. stock) with the move to the bigger wider tires?

[SickStroke6.0]

I think I lost maybe 1 MPG, but that's because I only do city driving. On the highway I don't see a change, maybe .5 MPG difference.

[75' forty]

rim choice will depend on tire size and rubbing.

[SickStroke6.0]

You want a wheel that has 4.5" backspacing.

[107stroker]

Originally Posted by Earl H

I just purchased a 2004 Excursion Limited. Its a Southern Car and is in excellent shape with relatively low miles @ 84K. I bought the vehicle for Wife to use as her DD. We needed something big and go Diesel for the F/E seemed to be the way to go. The vehicle currently has an 8" Superlift Kit with 37" Tires. The truck looks great and we love it (after many Suburbans/Yukons), however the "problem" is my F/E blows. I got 15mpg on the 700mile trip from GA to MI. City is just above single digits. I'm not sure if we'll even get 400 miles out of the 44 gallon tank in combined driving.

I am in the process of selling the lift kit and tires. I am planning on lowering it to stock or close to stock (2in.) and going with 18" wheels and 33" tires.

Questions: what is the widest tire that I can put on with the truck at stock height, without rubbing. I am considering the following tires: 325/60/18, 305/60/18 and 295/65/18: all are about 32.5-33.4" tall.

Anyone with estimates on how much F/E will improve with the tire change? Lowering? Will the 325 width yield much different fuel economy than the 295?

If you've done this or know of someone who has done this, please post your results.

Next step: tuner for F/E improvement.

Thanks in advance.

i have a 2005 excursion with 285/75/16 michelins. drove it from nc to pa and back to nc and got 19.8 at interstate speeds. think if i had driven 60 all the way it would have been over 20mpg.

[19558077]

your odometer is not reading anywhere close to what it should with 37's, are you calculating for that?

[Earl H]

Originally Posted by 19558077

your odometer is not reading anywhere close to what it should with 37's, are you calculating for that?

Yes. Its about 11/12 % off.

[Kracken]

I have an '04 Ex with stock size rims & tires but would like to lift and add larger rims etc..... I've heard that increasing tire size will change the gear ratio and tranny damage will result - bigger the tires, the more the change and quicker the damage. $3000 or so will get a gear ratio change to compensate but I'm not willing to shell outthat kind of cash.

Any experience or comments on this would be appreciated?

Thanks