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Old 11-11-2008, 10:55 PM   #1 (permalink)
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Join Date: Feb 2008
Location: Tooele, UT
Posts: 412

ZJ - '95 Jeep Grand Cherokee Laredo Upcountry
90 day: 20.57 mpg (US)

Neon - '03 Dodge Neon SE
90 day: 33.46 mpg (US)

S'Crew - '02 Ford F150 Supercrew XLT
90 day: 16.4 mpg (US)

Ranger - '90 Ford Ranger
Last 3: 28.02 mpg (US)

Not the Jeep - '03 Dodge Neon SE
90 day: 34.11 mpg (US)
Thanks: 7
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Tire size and FE with a Jeep

So I split this off my XJ thread.

When I bought my Grand Cherokee it had 235/75R-15s on it. While I was able to go most everywhere I wanted to go. But despite the factory 1" lift, I wanted a little more clearance. Mindful that I hadn't become concerned about FE yet. For reference, this Jeep has the 4.0 inline 6, 4 speed automatic, and 3.73 gears as part of a towing package. I sought this particular Jeep because of the lift, factory skidplates and tow hooks. I wanted to go offroad, didn't care much about FE, but then again, I was since I knew this got better mileage than a Wrangler.

Which leads up to now. The Jeep already had 235/75R-15s. They were All Terains. Last year I swapped up to some 30" tires, I got the set of tires and wheels for $80 and they made it over a year. Money well spent. They were also an All terrain type. I recently swapped to a different set of wheels with 31" tires, though they are more mud terrain tire this time. They were inexpensive, and I am cheap ($100 fro the wheels, $100 for the tires).

Pleasant surprise, as far as the taller tires for my ZJ, I noticed today on the freeway, I am spinning lower RPMs for the same speed than I did with the 30" tires. More important, it spins even lower than when I ran 235/75R-15s... Downside, the 31s are wider than either of the other tires, and they are just barely inside the fenders.

Progression, started with 235/75R-15s, about a 28" tire. Didn't like these wheels on my ZJ and they don't fit real well under my daughter's XJ, they rub when turning...

Yes, I was the lowrider of this group, and the smallest tires. While I made it through this set of trails this day, I realized I needed more clearance. Either bigger tires or some additional lift. Or both.

30s, these are the tires I was on to achieve Hypermiler status with the ZJ.

These weren't too bad in the snow, but not as good as the previous tires. But, they were great while they lasted for FE.

31s, Only been on for about 6 weeks, my kids were using the ZJ and aren't good for at FE. Though they do try.

Yes, I was stuck in this pic, and yes, it is a purpose built offroad park. Resting on a skidplate. It hangs too low, and it will be modified to be more flat and tucked up closer to the bottom of the Jeep. But first, it will be getting a 2" lift, replacing the front control arms too. I believe I have mentioned this lift frequently. Again, I do not need massive amounts of lift, or humongous tires. This should be sufficient...

So, I will see if I can get similar mileage. The bigger tires create a little more rolling resistance, I have them currently at 35 PSI. But they also reduce RPMs, so, will they offset each other? I'll see what I can do to smooth the bottom of the Jeep this year. I still want to build a front bumper that might slice the air better and provide solid protection as well (we have a little deer problem in the mountain pass I drive daily...)...

Anyone familiar with Totegotes...

Winter project...

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