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Would a tune or gear change help bad MPG with 35 inch tires?

PyrPatriot

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I second this...no offense to the Falken owners, but I HATED the stock Falken MTs...the 33" Falkens on stock rims weighed more than my 35" Patagonia MTs on my Procomp wheels. Tire and wheel weight make a huge difference and translate to "HP" gains without increasing actual power.
They ARE very tough though, which is why I chose them, sharp rocks make me weary. I never see them for sale used but find Patagonias for sale often enough. Suppose it is region/use specific. Rock crawling you wouldnt want heavy tires, mud/logging roads where garbage can be underfoot or creek beds with sharp rocks slicing K02s, yes you want thicker tires
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Trlr8tdd

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My 78 CJ7 with a 360 auto trans averaged 10 MPG. Drove it every day, 80 miles round trip. Worth every penny!
Adding 35ā€™s with 4.10 gears I knew Iā€™d take a MPG hit. Average 15.4 combined city hiway. Gets worse above 70, luckily the speed limits are 65/75, to keep gas in my tank šŸ˜Š
 

HorneyBadger

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I swapped to 35" tires on my Max Tow....I could feel a slight decrease in "off the line" performance, so I went to the dealer to have the ECU flashed.....My dealership told me they could only reprogram for 33" tires since it was not a Rubicon..... ??
Hmmm, Well as OP stated he bought the JT off the lot with 35's. If the dealer didnt do it then they may have voided their own warranty! And if this is true then Op's only recourse is the Tazer.
 

cgflyer

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They ARE very tough though, which is why I chose them, sharp rocks make me weary. I never see them for sale used but find Patagonias for sale often enough. Suppose it is region/use specific. Rock crawling you wouldnt want heavy tires, mud/logging roads where garbage can be underfoot or creek beds with sharp rocks slicing K02s, yes you want thicker tires
I just bought my second set of Pat's...first set had 32,000 miles on them almost with close to half tread left...sold them only to go to 37's, but point is taken about a tough tire, but I did not like the ride at all...the Pat's are very smooth, quiet and grippy. I personally have not seen a bad review on them...not to hijack the OP's post with arguments about tires haha...but I think it fits with my previous point about to each their own...EVERY Jeep is different because every Jeep has a different driver and each driver has their own preferences and experience. Some may not know that their tires suck because they have zero experience in which to compare. If I was getting 14 mpg in my Gladiator, I would be concerned because it is contrary to my past experience...I think OP should be concerned because most Gladiator owners are doing better than that. I'm still in the 17-18 mpg range with 37's on stock 4.10 gears and a MT.
 

shrinkhead

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every inch you go up in tire size costs one MPG ha ha. I am getting 13.5 with 35s and 2 inch lift and there's nothing out there to fix it. On the upside you can now drop a V8 in and retain the same mileage.
 

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PyrPatriot

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I'm still in the 17-18 mpg range with 37's on stock 4.10 gears and a MT.
What kind of terrain and weather do you normally drive through? I can get 17-18 on flat-ish surface but my area is almost entirely hills.
 

mstrav73

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I've been arguing on one of the FaceBook Jeep Gladiator sites with some idiot about that.....He told me he put 37's on his Gladiator Overland (.373 gearing) and didn't notice any performance decrease ! I told him he was "clinically dead" !
Heā€™s just being stubborn, the gladiator doesnā€™t have huge power or a turbo to easily overcome the affect of bigger tires and lifts unfortunately. They do look dam good lifted but mpg absolutely goes down unfortunately as a result, I own (2) of them and results are the same
 

shrinkhead

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Heā€™s just being stubborn, the gladiator doesnā€™t have huge power or a turbo to easily overcome the affect of bigger tires and lifts unfortunately. They do look dam good lifted but mpg absolutely goes down unfortunately as a result, I own (2) of them and results are the same
So. Performance is about the same on the auto but the engine is running with more rpms producing more power to do the same task that required less power on 33s. That ruins MPGs but I get here is coming from
 

GrayGoose

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I have 37's and 5:13 gears - I average 16 mpg unless I get on the hwy....at 70 + economy drops to 13 mpg (just did a 100 mile run and reset trip - cruise set at 72 and averaged 13 mpg).

You would know if it is not calibrated for tire size because your speedo would be off.

The gear swap was huge factor in performance, as it now uses 7th and 8th gears but in my experience minimal affect on fuel economy.
 

Orange01z28

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What's "crap?"

I get about 17 city and 20 highway with 3.73s, 35s, and a recalibration

My average is usually right around 19 since I do more highway driving than city
 

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3:73 are not the right gearing for 35" if your interested in milage.
Regear.
This is the main reason I opted for the Max Tow option. 4:10 gears so I could easily run 35's. I've seen very little milage drop. 19 city and as high as 20 highway if I stay under 65 MPH
Man, how do you see 19 city? I only see 15.8-16mpg city with out stock JTR
 

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Man, how do you see 19 city? I only see 15.8-16mpg city with out stock JTR
I get 19 city as well in the summer. I'm around 18.4 right now running winter gas. I'm running 315 70 17 bFg KO2s
 

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3.73's / 2" Mopar, Steel bumper / 35's / JScan recalibrated

Louisiana....flat....around 14.5/15 mpg

Tailwinds are nice when going 65 and below for I can sometimes see 7th gear..and 17-18mpg

Took a 2,100 mile trip this past fall...maintained the speed limit the whole way...65-70-75mph range...avg 15.9mpg.


Would love to go 4.56 if I could find someone remotely local to do it.
 

Rubiwoo

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oh, it's probably the BFG's. They are lighter than the Wildpeaks.
 

guarnibl

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oh, it's probably the BFG's. They are lighter than the Wildpeaks.
Yep. Tire size is a single variable that isn't solely responsible in determining mpg.

OP, you have Black Rhino Wheels (50 pounds?) and extremely heavy 35" tires (77 pounds). Assuming that is correct, that combination weighs more than some wheel tire setups on 38/40's. Consequently, there's your root cause. As far as fixing it, you probably won't completely unless you shed unsprung weight. If it were me, I'd probably try to sell the wheel tire setup and use stock Rubi take offs with a spacer and a 35" (315 -- which is a 34 1/2 and C rated) KO2. Probably don't need to re-gear then, and your calibration from dealer would also stay correct (assuming they actually did it).
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