Best Tire Size for TJ 4.0 Auto w/ 4.11 Gears??? - Jeep Wrangler Forum
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Old 01-09-2017, 12:15 AM
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Best Tire Size for TJ 4.0 Auto w/ 4.11 Gears???

I have recently bought an 02 TJ Wranger X (4.0 i6, Auto, New 4.11 Gears, 2.5" Suspension Lift). Using 1.25" wheel adapters, it currently has 275/70R18 tires on 18" JK wheels (33" tires). I am new to the Jeep world and all the options make my head spin. This Jeep is going to be my daily driver now so I am curious to hear what will be my best tire size option for Daily Driving/Highway Driving given its current Gears and Lift. What is going to give me the best performance so I am not over working the engine with constant high RPMs and giving me the best gas mileage I can achieve ( i know Jeep are not known for gas efficientcy but I still want the best i can get). And will it be best to find a different wheel (TJ 5x4.5) or can I still use the JK wheels without issues?

Thanks

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Old 01-09-2017, 12:48 AM
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I found this
Gear Ratio Calculator - Choose the right Gears for your Tires!
according to it i need 34" or 35" tires for the best MPG ans Highway Driving. Is that right?I I was thinking I might need a smaller tire but with different gears that changes.....
With only a 2.5" Suspension Lift can I go up to 35" and be Ok? And can I stick with the JK Wheels and my 1.25" adapters or will i be better off going with a TJ wheel?

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Old 01-09-2017, 01:47 AM   #3
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It really depends on your transmission. Automatics are much more picky with gearing than manuals are. Also, you don't want to run too low RPMs on the highway. The power of a Jeep ending is in the mid to high 2k range, so that is where you'd like to be at when driving at highway speeds. Yes, lower RPMs may give you better MPG, but performance will be much worse and if it's too low it could hurt MPG as well.
I will let others chime in that have experience with the transmission in your Jeep and the gearing required for your tire size.
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Old 01-09-2017, 07:07 AM
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That matches up with the numbers on the link that i found. The chart there says with 34" 2640 RPM and 35" 2565 RPM @ 65mph.

Now I am wondering if I can put 35" tires on my Jeep with only a 2.5" suspension lift....anyone here doing that?
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Old 01-09-2017, 08:39 AM   #5
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Now I am wondering if I can put 35" tires on my Jeep with only a 2.5" body lift....anyone here doing that?
no. I am on the low end with 3" front springs, 2" rears, 1.25" body lift, and highline fenders with 35's.

wouldnt recommend more than a 1.25" BL either way.


heres a more in depth gear calculator
http://www.grimmjeeper.com/gears.html
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Old 01-09-2017, 09:38 AM
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sorry i ment to say 2.5" suspension lift. Not sure if that makes a difference. I have now made the correction in my previous statement.
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Old 01-09-2017, 10:18 AM   #7
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if you add a 1.25" body lift and the appropriate bump stops to keep your tires out of your fenders, but you'd be losing uptravel unless you add more lift or raise the fenders.

have you prepped for 35's by upgrading steering, brakes, and planning the proper gears?
d44 or d35?
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Old 01-09-2017, 10:22 AM
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the gears in it are new 4.10 front 4.11 rear. i know there is a RC steering stabilizer on it. havent done anything to the brakes yet.
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Old 01-09-2017, 10:24 AM
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Also i am not planning to do any trail or off road driving with it.....if that makes any differnce in all of this.
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Old 01-09-2017, 10:37 AM   #10
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To run 35's...
You need to make sure your rear axle is a D44 (not a D35), or install a ford 8.8
Your stock tie rod is not stong enough for 35" tires. It needs to be upgraded to at least a zj tie rod. A currie-lync steering system is better.
Your front brakes need to be upgraded to a minimum of centric rotors and black magic pads.
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Old 01-09-2017, 10:48 AM   #11
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To run 35's...
You need to make sure your rear axle is a D44 (not a D35), or install a ford 8.8
Your stock tie rod is not stong enough for 35" tires. It needs to be upgraded to at least a zj tie rod. A currie-lync steering system is better.
Your front brakes need to be upgraded to a minimum of centric rotors and black magic pads.
x2
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Old 01-09-2017, 01:04 PM
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so.....basically I should stick with running the 33"s - 31"s..... unless i want to drop a lot of cash to make upgrades just to run 35"s???
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Old 01-09-2017, 01:49 PM   #13
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yep, regular cost to run 35's is $5k-$10k
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Old 01-09-2017, 02:28 PM   #14
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yep, regular cost to run 35's is $5k-$10k
Yup. I looked into this when trying to plan what I wanted to do with my Jeep. Even running 33s can require some upgrades which will add up as you go. I decided to stick to a modest 2" lift and 31s (maybe 32s in the future) and just enjoy it.

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