Dream Girl

Lots of threads about "what gear should I go with" on the JK-Forum,
But nothing about "proper gearing" and "MPG" in depth discussions

The Question:
Will going bigger always reduce the MPG, or, just as the guy on this thread suggested - with the proper gearing it will actually improve it!?

So, Just for example, *so we can start our in depth discussion on this subject
- I have a stock JKU Rubicon, and thinking to go bigger, 33.. 35? 37!?
not sure yet as the MPG will play a big factor,
DD, 50% HWY, 40% City & ~10% medium off road.

Pluke the 2

the first step is knowing what size tire you're going to be with for the rest of your life. there really isnt a solution to the answer.

way to many variables, driving habits, tires, trannies

and when you say your 20% off road... that is a lot of off roading especially if the jeep is your dd.

Rubicorn

Hi,

Nice to see someone from Winnipeg. There are lots of us in town with real mileage numbers to share. I have 35" bfg at's and definitely experience a drop in mileage (went from about 22mpg on highway at 95kph to about 18). A friend (also in winnipeg) went to 37" kevlars and 5.38's and his mileage is poor as well (but better than when he had stock gears). Another member has 35" duratracs (standard trans) and his mileage dropped too.

Getting better mileage from taller tires in town may be possible if you drive very, very conservative. On the highway it's all about wind resistance and the poor little 3.8 loses every time, no matter what the gearing.

You can run 35's and 4.10's, even with an auto, but regearing helps more than most think.

Dream Girl

Well, I am leaning towards 35, and maybe I was exaggerating on the 20% off road...

Pluke the 2

lol, assuming the JK is your dd 20% would be 6 days out of the month.

Noxian

Even with gears you will increase the weight of your tires, and your rolling resistance so you will lose abit of MPG even after regearing. But after re gearing you can regain some of your lost power and and return the MPG back to as close to stock as possible.

5.13s seems to be pretty common for 35s from what i have read.

another Winnipeger

Noxian

yeah with a auto and 4.10s you lose the final drive ratio of your OD which is a huge loss on the highway for fuel economy.

jeep2007

Bigger tire= more rolling ristance=less MPG. I run 35X12.5X17 on 4:10 gearing. It is a daily driver. Wiith OD off, does fine, but definetely needs geared to 5:13 at least to bring the RPMs back to "normal", as well as MPG. I average 13-14, but regeared I will gain maybe 2 more MPGs. I have all the performance mods available less the programmer so I assume it would be even lower without them.

Just my 2 cents. Hopefully Panman will chime in and Jpop.

JK-Ford

I'm not trying to be a "wise guy". Just curious But would you recomend a different tire and gear set for a rig with only 10% off road time verses 20% off road time. The only reason I bring this up is because I am interested also. The Jeep is designed for a lot of different terrains. And just like the OP, my rig is a DD also. And I would rather have a gear set that is good for all terrains. And not best for any one specific.

Noxian

It really depends on what kinda wheeling you do, you could wheel stock I did it for 3 years in my TJ Rubicon, and I am thinking I may wheel stock for the next year with my JKU Rubicon. Anything after that takes away from its DD ability IMO.

On TJs 33s seemed to be the best for a true DD and some light to moderate off roading.

On JKs it seems 35s are the new 33s.

That being said its still a Jeep and they are very capable out of the box.