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Old 09-05-2007, 08:20 PM   #1
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tires vs gears (what will it feel like) formulas...

Just got my "offroad adventures" magazine and it has few interesting equatoins to determine good gear ratios or what it will feel like or etc... I'll be using my rig as an example to explain it better.. i have 30" tires with 3.73 gears and want to go to 35" tires.

Effective overall ratio...
..what will it feel like after installing different diameter wheels on the same gears.

old tire diameter / new tire diameter x axle ratio = what ratio it will feel like, not taking tire weight difference into consideration.

ex... 30/35 x 3.73 = 3.19:1

so when i install 35s on my rig it will feel like as if now with my stock 30s i install 3.19:1 gears.


Equivalent Overall Ratio
...aproximately best gear ratio after installing new size tires.

new tire diameter/old tire diameter x original gear ratio = new gear ratio ... not taking tire weight difference into consideration.

35/30 x 3.73 = 4.35:1

so ideal gear ratio for the new tires would be 4.35 (again tire weight difference will change that)

Hope that gives some people heads up on what to expect.

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Old 09-05-2007, 10:14 PM   #2
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now all youve got to do is find someone who makes 4.35 gears

"ideal" though? ideal for me would be to go the lowest you can. If your paying for gears then "get the gears!"... which would be 4.88 for a d30 setup

*edit: math makes my head hurt

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Old 09-05-2007, 10:22 PM   #3
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Quote:
Originally Posted by ygohome View Post
"ideal" though? ideal for me would be to go the lowest you can. If your paying for gears then "get the gears!"... which would be 4.88 for a d30 setup

*edit: math makes my head hurt
Agree - and if your running anything larger than say, 37's on 4.88's(considering that your using a D30)... get new axles to get lower gears!
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Old 09-05-2007, 11:48 PM   #4
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Don't forget to factor in Manual vs. Automatic transmission. I am running 3.73's with 35's and with my auto it has better pickup and power than a 3.19. Now if you had a manual I would agree with your calculations.
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Old 09-06-2007, 12:04 AM   #5
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straight from the jeep porn here.. not mine..
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Old 09-08-2007, 10:42 PM   #6
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Your math looks to be spot on. Standard gears available are: 4.10, 4.56, 4.88, and 5.13.

For 35's I recommend 4.56's. 4.88's are also a very good choice since they'll give you more torque on the low end, but the size of the tooth between 4.56 and 4.88 makes me lean towards 4.56's still. Beside the fact that they'll give you better milage on the road (by comparrison).

As to the feel: you should be pretty close to the stock feel when on and off road.

Just be sure and get the proper speedo gear when you are done. For 35's with 4.56, you need a 36 tooth and for 35's with 4.88's you need 39 tooth (part numbers 52067636 and 52067639 respectively).
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Old 09-09-2007, 03:18 AM   #7
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btw i know the gears and all that so i'm not asking for help here altough thank you anyhow . As i said its just something i saw at my jeep porn and thought i should post it here.
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Old 06-05-2011, 01:05 AM   #8
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for clarification, please hold the head hurting math for a moment and "agree" or "disagree" with the following please.

For a 2000 TJ 5 spd with 4" OME lift and 33" tires the 4.88 gears are best for DD stock performance.

Thank you for the help

Coyote
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Old 06-07-2011, 10:20 PM   #9
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2.5 or 4.0 ?

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