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Unread 12-21-2009, 04:19 AM   #1
mudman1
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is it possible to adjust the speedometer for bigger tires?

i read when you put on bigger tires, the speedometer will be inaccurate.

is it possible to have the speedometer adjusted? if so, could myself or the average mechanic do this? and how much would it cost? the jeep is a 2007 wrangler.

also, when the speedometer is inaccurate, does it create inaccurate mileage for the car too? or is just the speedometer incorrect? if the odometer would be incorrect too, is there a way to adjust both the speedometer and odometer?

thanks


Last edited by mudman1; 12-21-2009 at 04:31 AM..
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Unread 12-21-2009, 04:46 AM   #2
mudman1
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i think i found the answers here:
Changing Your Jeep Speedometer Gear

but i have a new question. how do i find out my "R&P"? that info + new tire size is needed to find out which new speedometer gear i need.

and what does "R&P" stand for?

thanks
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Unread 12-21-2009, 05:28 AM   #3
SETXWarrior
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Your JK does not use the gear, it's electronic and needs to be re-programmed.

There are several brands that provide different levels of functionality and priced accordingly.

I used the Pro Comp Accu Pro that only corrects tire size and gear ratio, and was less than $200. Other types are made by SuperChips and AEV.

Yes, your odometer will be off until it is re-programmed.
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Unread 12-21-2009, 06:26 AM   #4
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I used the AEV procal. Think it was $130. That did the trick for me and also fixed a couple other issues. Great tool to have for tire size and many other things.
Check it out!

American Expedition Vehicles - Wrangler ProCal Module - Additional Vehicle Features and Calibration Tool
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Unread 12-21-2009, 07:26 AM   #5
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What year did they stop using the gear and switch to eletronic? I have a 2006 TJ with six speed transmission.
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Unread 12-21-2009, 08:20 AM   #6
Seanie
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Quote:
Originally Posted by mudman1 View Post
i read when you put on bigger tires, the speedometer will be inaccurate.

is it possible to have the speedometer adjusted? if so, could myself or the average mechanic do this? and how much would it cost? the jeep is a 2007 wrangler.

also, when the speedometer is inaccurate, does it create inaccurate mileage for the car too? or is just the speedometer incorrect? if the odometer would be incorrect too, is there a way to adjust both the speedometer and odometer?

thanks
It depends on the size of the wheels as well. If they are 32 inches or smaller, the dealer can do it for like 50 bucks, but if they're over 32's, it'd probably be better just to order something to do it yourself.
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Unread 12-21-2009, 09:37 AM   #7
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Originally Posted by nellanaesp View Post
It depends on the size of the wheels as well. If they are 32 inches or smaller, the dealer can do it for like 50 bucks, but if they're over 32's, it'd probably be better just to order something to do it yourself.
Why would that matter? It's a computer. If they can adjust for 32's they should be able to do 33's, 35's, even 40's.
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Unread 12-21-2009, 10:52 AM   #8
DeepSky
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Originally Posted by Scooter_Trash View Post
Why would that matter? It's a computer. If they can adjust for 32's they should be able to do 33's, 35's, even 40's.
From what I understand the dealer's equipment (whether software or hardware) limits them at 32" because that is the largest tire that comes on the Wranglers from the factory.
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Unread 12-21-2009, 11:45 AM   #9
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From what I understand the dealer's equipment (whether software or hardware) limits them at 32" because that is the largest tire that comes on the Wranglers from the factory.
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Unread 12-21-2009, 02:07 PM   #10
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haha, looks whose talkin! Plus, I've been busy today...for the most part...
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Unread 12-21-2009, 02:11 PM   #11
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AEV procal worked for my regear and 39" tires. also recalibrated the steering for dead center so the ESP didnt go crazy. i recommend it since it was easy to do, quick, and 0 issues with my build.

5.5" RK coil over, 5.13 gears, 39" tires. on stock v6 and 6 speed.
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Unread 12-21-2009, 02:14 PM   #12
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The odometer will be off as well as the speedometer when you add larger tires. As mentioned above you will need an aftermarket programer in order to change the tire size in the computer with anything larger than a 32. I went the AEV Procal route, only 129 and worked very well. R&P is ring and pinion which refers to your gear ratio. Depending on the model/options you have it will be 4.10, 3.73 or 3.21 I believe.
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Unread 12-21-2009, 04:22 PM   #13
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