gas mileage loss with 33's?

[Purpelhaz3]

I'm planning on putting 33x11.50's on my '95 Xsport after a body lift and TT+shackles lift.... Right now i have 29" A/T's with the 3.73 gears and flowmasters..as of now, i get around 15-17mpg, how much do you think that will drop with the 33x11.50's on there and not changing the gearing?

I also plan on taking out the front bumper and replacing it with a tubular on (bad aerodynamics) how much do you think that will affect mpg also?

 

[jimbo74]

size and weight of everything will dramitically decrease mileage... 3.73s. with that big a tire and with a possibly heavier then stock bumper is going to drastically and negatively effect mileage... since there is no accurate way to guage it due to driving conditions such as road conditions, location, driver habits, there is no way to guage what your mileage might be... its going to suffer though, 33s is best suited with a 4.10 gear ratio or a 4.56 gear ratio

 

[Purpelhaz3]

size and weight of everything will dramitically decrease mileage... 3.73s. with that big a tire and with a possibly heavier then stock bumper is going to drastically and negatively effect mileage... since there is no accurate way to guage it due to driving conditions such as road conditions, location, driver habits, there is no way to guage what your mileage might be... its going to suffer though, 33s is best suited with a 4.10 gear ratio or a 4.56 gear ratio

I get 15/17 mpg driving 50% city 50% highway, not heavy on the pedal but not at all easy on it. The bumper is just going to be something of the likes of a smittybuilt tubular bumper that you see everwhere. So with that information, what would be your guess as to the fuel economy loss..... i honestly have no clue, but i really want to know because if it drops it to say 13/15 i can justify the purchase, but it it drops below say 13mpg i can't financially justify it.

Also, what would the INCREASE be in fuel economy with lower gears? possibly back up to my 15/17?

 

[jimbo74]

with gear it is possible to get back up to factory powerband specs.. however you must realize it might never get that high due to the increased weight......

 

[Purpelhaz3]

with gear it is possible to get back up to factory powerband specs.. however you must realize it might never get that high due to the increased weight......

Like i said, i have 29x10.50's right now with 3.73 gearing, do you you think going to say a 31x11.50 rather than a 33's might save me the trouble of needing to re-gear for fuel economy?

 

[jimbo74]

31s isnt as drastic but again, mileage will go down and there is added weight

 

[Mbrooks420]

If you go with 33's you will likely lose more than 2 mpg. Plus with the mileage loss there will be power loss as well. With 31's you won't need a BL and tt and shackles. Before thinking regearing, be prepared to spend upwards of a ggrand.

 

[unclemeat]

When I lifted mine I went from 30.5x9.5 AT to 33x12.5 mud tires with 3.73 axle ratio. Mileage went from about 18 to 12. I regeared to 4.56 and mileage is between 16 and 17 mpg. Mostly city driving.

Congrats Jim she looks just like you.

 

[jrgaylor]

unless you regear you will avg ~11-12 MPG

 

[CDW6212R]

unclemeat, that is promising. I went from 29" 17's to 30.5" 18's. The weight difference is about fourteen pounds each. They have cost me at least 1.5 MPG, from almost 17MPG to just over 15MPG.

Weigh the old and new tires. The weight is the biggest factor, and you can search for lighter wheels and tires. It would be worth the time invested. Good luck,
DonW

 

[Stic-o]

I use to get 15-17 stock. Now with 33's I get 11-12 on the street and If I do all highway I can get 15 out of her. Still runing 3.73's. The key is a cat-back It really helped alot!

 

[becker69]

I know we are set up differently (I have an SOHC) but the numbers are surprisingly similar; New I had 255 70 16's (30 x 9" or so) and averaged almost 18mpg (all city driving) then I went to lighter 15x8 eagle wheels at 17 lbs each or so and BFG 32x11.50 AT/KO's (over 45 lbs a tire) and after my grill guard/lights (adding 45+ lbs to the front bumper) now I average 15mpg city.... with 4.10 gears. I will have to research the benefits of cat-backs relating to mpg/power trade offs.


edit - for what it's worth pro-comps site list their AT tire size/weight as:

30x9.50x15 - 36 lbs
31x10.50x15 - 41 lbs
31x12.50x15 - 42 lbs
32x11.50x15 - 44 lbs
33x12.50x15 - 56 lbs

Makes me think more about my brakes as I decide whether to try to go to 33's.

 

[dreamr]

unless you regear you will avg ~11-12 MPG

That is where I am at