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Old 01-14-2011, 09:18 AM   #1
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Gear ?

Is their a calculator that can tell me what RPM i will be at with the tire size and gear. Right now i have 265 75 16 tires with 3.21 gear. I plan on going 35s and im going to put new gears in. I want to know what RPM i will be at with 4.10 and 265 75 16/33s tires. Also 4.56 with 265 75 16/33s. The tires i just put on so it will be a lil while before i get bigger tires. Im going to do the gear install in the next couple weeks 33s will be as big as i go so what is your opinions on the gear 4.10 or 4.56. Thanks

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Old 01-14-2011, 09:43 AM   #2
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Well 4.10 is 27.7% greater than 3.21, and 4.56 is 42.1% greater than 3.21, so just take your current RPM's and multiply by 1.277 and 1.421, respectively to get the new RPM's. And since your current tires are 90.4% the diameter of 35's, to calculate your RPM's with 35's, multiply again by 0.904.

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Old 01-14-2011, 09:56 AM   #3
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Quote:
Originally Posted by yomondo View Post
Well 4.10 is 27.7% greater than 3.21, and 4.56 is 42.1% greater than 3.21, so just take your current RPM's and multiply by 1.277 and 1.421, respectively to get the new RPM's. And since your current tires are 90.4% the diameter of 35's, to calculate your RPM's with 35's, multiply again by 0.904.
Now who said math was hard!
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Old 01-14-2011, 10:05 AM   #4
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My '08 JKU with 4.10 gears/auto/OD runs 2000 rpm at 70mph-in OD and about 2800rpm at 70mph-outta OD

Also depends on your airpressure and installed height !!

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Old 01-14-2011, 10:20 AM   #5
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Old 01-15-2011, 12:03 PM   #6
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maybe this would help

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Old 01-16-2011, 12:41 AM   #7
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What MPH is this at
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Old 01-16-2011, 01:01 AM   #8
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This should help

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Old 01-22-2011, 02:04 PM   #9
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I am getting ready to go with 4.56 gears in my 2011. I have 35" tires and the shop stated with these gears, and my tires, this is going to be VERY close to what it was from the factory with the smaller tires. ...but, I only drove the Jeep for 600 miles, then lifted it, so I really don't remember what "factory" was.

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