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Old 11-07-2012, 09:44 PM   #1
Join Date: Nov 2012
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Tire Size - MPG

hey y'all. I'm looking to trade up to bigger tires. I have the BFG 32" on my 07 JK Rubicon and I was to go to the Falken Wildpeaks on a 35". Has anyone done this while tracking MPG? I assume it will go down but I saw a chart, and it seems a little crazy, but it showed that with 4:10's the gas mileage would be better on the highway because the cruising rpm would be lower.

Please discuss!
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Old 11-08-2012, 06:38 AM   #2
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First of all, from experience, going from a tire that measures 31" on the Jeep to a tire that measures almost 34" on the Jeep is a big change. Your acceleration, braking, and power will take a nose dive. This means your fuel economy will also take a nose dive. I expect that if you drive it exactly the same, you'll lose 2-3 miles per gallon.

Second, choosing the Falken tires hurts even worse because they are some of the heaviest tires on the market. And all that weight is just brutal on fuel economy and drivetrain parts. The Falkens vs. other brands is worth about 0.5 to 1.0 miles per gallon.

So in the end, you're going to lose a signficant amount of MPGs. Currently, every 1 MPG is worth almost $20/month to the average driver in the U.S. So, losing 3.5 MPGs could be like adding a $75/month payment to your checkbook.

But, it will look cool.

~Lots of modded Jeeps and a Toyota 4Runner~
My favorite quote from the press release.. sad but true: "Chrysler claims its products, especially the Jeeps, can handle all sorts of terrible conditions, churning through muddy swamps, climbing mountains, and crossing rivers. Turns out they cannot even handle a car wash."
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Old 11-08-2012, 07:33 AM   #3
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your redeaming point is you have 4:10 gears. so moving up to a 35 gearing wise will work but... ya always is. the taller the sidewall the higher rolling resistance the worse the fuel economy. have you noticed the trend to big wheels an small tires? there ya go. tread face arch also has an effect as well as unspung wieght. so for you run a Nitto Alterrian. they are lighter then their brother Toyo, but very flat tread, rolls very easy and great road manners and off highway performance on lighter vehicles. still run the 35psi in them but don't expect them to work like a mudder as they are not.
what you gain in gearing will go away from the other factors. remember your frontal area is larger so if you drive fast you might find a drop in fuel econ at 75. overall i would do the 35's
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Old 11-08-2012, 09:47 PM   #4
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Recently upgraded my 03 rubicon from 31" goodyear mtr's to 33" toyo mt's. Gas mileage dropped from 17-20.5 down to 14-16. My jeep is a 5spd/4.10.
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Old 11-08-2012, 09:56 PM   #5

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make sure when figuring mpg that you are taking in consideration that larger tires are going to show less miles traveled on the odometer so if you are figuring mpg by dividing miles by gallons it is going to show less mpg then actaul.
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Old 11-09-2012, 09:36 PM   #6
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I was doing the conversion with mine.
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Old 11-10-2012, 06:45 AM   #7
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I was hoping for the same thing.. Less RPM more MPG.. Well it didn't work out for me, lost a couple mpg with my 285-70-17.

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Old 11-11-2012, 01:04 AM   #8
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smitty what gear ratio you running with your 285/70 17,....i got that dilemma, got tha same but on r16 and need a good regear to make it a dailey driver
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Old 11-11-2012, 06:21 PM   #9
Join Date: Oct 2011
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Running 16x8.5 Alloys with a set of 295/75-16's (34's) Nitto Terra Grapplers (AT)... 4.10 gears...

From the 32" stock Rubicon tires.

Stock setup per tire: 72lbs
New 34" setup per tire: 78lbs.

Gas mileage is MARKEDLY improved on the highway. However, getting a larger diameter tire moving in stop and go is going to take a beating.

I hit 22mpg on the highway last night, on my first trip on the new AT's.

*YES I set the proper tire size in the ECU and confirmed the speedo was accurate.

What you have to realize is an MT is ALWAYS going to drop gas mileage over a similarly sized AT!

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