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Old 08-15-2013, 10:37 AM   #61
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I factory ordered my 12 Rubi manual trans last year and my only gear choice was 3.73 and 4.10's did I miss something? I don't think your Rubi is 3.21's. Hope your milage goes above 12MPG thats crazy!

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Old 08-15-2013, 01:04 PM   #62
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Originally Posted by dukedallas View Post
I factory ordered my 12 Rubi manual trans last year and my only gear choice was 3.73 and 4.10's did I miss something? I don't think your Rubi is 3.21's. Hope your milage goes above 12MPG thats crazy!
You should probably read this whole thread.

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Old 08-15-2013, 07:48 PM   #63
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Agree, just make sure to actually measure your new tire height when you program the procal, and don't go with what the calculated # "should be". Many 33's are 32's, 35's are 34's, etc...
Tire height is measured unloaded. Procal requires you to enter the loaded height. For example, my 32" tires measure 31 on the ground. That's what I had to enter with the Procal to get the speedo to read accurately.
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Old 08-17-2013, 12:35 AM   #64
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Agreed with above, with tire height. However, I als used my GPS to fine tune the procal setting too. I had to dial the procal a few times until the GPS speed matched.
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Old 08-17-2013, 12:51 AM   #65
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Agreed with above, with tire height. However, I als used my GPS to fine tune the procal setting too. I had to dial the procal a few times until the GPS speed matched.
^This too. Good point. I got mine on the second try, GPS tweaked.
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Old 08-29-2013, 11:24 PM   #66
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so i went to the dealership and they said they dont recalibrate the speedometers anymore and if i do it will void the warranty so if something is to go wrong in the future they will say its because the oversiZe wheels .. the guy just told me to leave it like that and try to drive cruise especially taken off from stops i guess i will try to drive slower
Your dealer is full of BS. Nothing voids the warranty unless it can be directly tied to the failure. I hardly think recalibrating a speedo will do damage. You might also consider going to a dealer and their parts dept and getting a VIN report. Better than a window sticker because instead of listing all the standard stuff and then options that replaced them, it lists specifically what YOUR Jeep has along with the RPO codes including gear ratio which I know you've already found. I would also recommend keeping a copy of the Magnusson/Moss act in your Jeep. I've had to pull that out before because a dealer didn't want to warranty something because of aftermarket mods.
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Old 08-29-2013, 11:33 PM   #67
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I dont trust the gauge to tell me actual MPG. I roll around on 37's getting 16.1 in my 13JK, my friend rolls around on 33's with no lift on her 12JK and she gets about 15. my theory? the display is different. we are both calibrated for our gears and tires and I actually have more miles on my rig.
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Old 08-29-2013, 11:36 PM   #68
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Don't be mean to panthermark, he is as sharp as a tack.

Adding rubicon stickers is your choice, but everyone on this forum will know you're a Sport in disguise if we see you on the trails. You'll get more respect for being proud of what you have instead of pretending you achieved something you haven't...like people who claim to have run marathons but get winded when they go up a flight of stairs. I suggest replacing the rubicon sticker with something you like, see "SKYWALKER," or "RED ROCKET."

I could derive angular momentum and rotational speed for you to help define why your on-board computer is confused, but it's easier just to say "crap in, crap out." You need to make sure your vehicle configuration is being accurately processed by your computer, so it can make vital decisions (most of which are much more important than calculated fuel economy). Sensor outputs are only as valid as the computer's understanding of what it is seeing.

Good luck.
seriously considering getting BOOTY PATROL on my hood.
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Old 08-29-2013, 11:46 PM   #69
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I get about 16 - 17 driving arround town and to work and back. None of my few mods would effect my gas milage so thats prety much stock setup
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Old 08-29-2013, 11:52 PM   #70
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seriously considering getting BOOTY PATROL on my hood.
I approve.
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Old 08-29-2013, 11:58 PM   #71
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seriously considering getting BOOTY PATROL on my hood.
Ahhh! Wish I'd thought of that. Not doing it cause I don't want to steal your idea, but that's awesome. Wonder how the wifey would feel about it lol.
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Old 08-30-2013, 01:25 PM   #72
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by calibrating my speedometer is going to give me better mpg's?

Calibrating your spedometer will not affect your gas milage.

It will give you the correct information to more accurately calculate the gas milage you are getting.
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Old 08-31-2013, 01:56 PM   #73
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Originally Posted by redrockculichi View Post
by calibrating my speedometer is going to give me better mpg's?
This will only help if your using your on board computer to tell you the MPGs as it is giving you wrong info because the tires have changed. but if you manuely calculate based on a fill up and do the math it wont matter. and to the jerk giving you crap about the rubicon sticker: I would say throwing a sticker on a jeep and not spending the extra 10k is pretty smart. I think its dumb when somone OVERPAYS for a rubicon only to replace the wheels ,tires and suspension is the dumbass- alsoThe 3:21 gearing means its geared for the towing package and highway use, investing in re-gearing would take you years to recoup the money in MPG's. I run the same size tires with a 2 inch lift and get 14.5 but I have the 2010 motor-
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Old 08-31-2013, 02:59 PM   #74
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You can't hand calculate it when the odometer is off. You''l have to recalibrate the speedometer so that the miles will read correctly.

A larger tire makes less revolutions per mile. Therefore the speedometer reads slower than you are actually traveling. This results in less miles on the odometer than were actually traveled. This will cause you to get the impression that you are getting less MPG than you actually are.

Recalibrate, then you will know what speed you are going and exactly how far you have traveled. When you know exactly how far you've traveled you can accurately calculate MPG. No other way, unless you use a GPS.

3.21 is not geared for towing. That ratio is only for better MPG on the highway. 3.73 and 4.10 are much better for towing, but worse for fuel economy. This is often an area of confusion. lower gears (numerically higher i.e. 4.10 is lower geared than 3.73) are better for towing, slow speed trail crawling and around town driving.
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Old 08-31-2013, 06:40 PM   #75
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Originally Posted by ctvenegas View Post

This will only help if your using your on board computer to tell you the MPGs as it is giving you wrong info because the tires have changed. but if you manuely calculate based on a fill up and do the math it wont matter. and to the jerk giving you crap about the rubicon sticker: I would say throwing a sticker on a jeep and not spending the extra 10k is pretty smart. I think its dumb when somone OVERPAYS for a rubicon only to replace the wheels ,tires and suspension is the dumbass- alsoThe 3:21 gearing means its geared for the towing package and highway use, investing in re-gearing would take you years to recoup the money in MPG's. I run the same size tires with a 2 inch lift and get 14.5 but I have the 2010 motor-
Calm down bud. Easy with the name calling.
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Old 09-02-2013, 04:25 PM   #76
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Originally Posted by JKBrad View Post
You can't hand calculate it when the odometer is off. You''l have to recalibrate the speedometer so that the miles will read correctly.

A larger tire makes less revolutions per mile. Therefore the speedometer reads slower than you are actually traveling. This results in less miles on the odometer than were actually traveled. This will cause you to get the impression that you are getting less MPG than you actually are.

Recalibrate, then you will know what speed you are going and exactly how far you have traveled. When you know exactly how far you've traveled you can accurately calculate MPG. No other way, unless you use a GPS.

3.21 is not geared for towing. That ratio is only for better MPG on the highway. 3.73 and 4.10 are much better for towing, but worse for fuel economy. This is often an area of confusion. lower gears (numerically higher i.e. 4.10 is lower geared than 3.73) are better for towing, slow speed trail crawling and around town driving.
Thanks for the clarification....
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Old 09-19-2013, 09:18 AM   #77
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hate to be the guy that points out the obvious but an alignment, and tire pressure are huge contenders as well.
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Old 11-13-2013, 09:15 AM   #78
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I'm in the same boat. I bought my 2013 JK Sport (automatic) that was bone stock with 8,000 kilometres on it a few months ago and I was disappointed to see my MPG plateaued at 12-13 after I changed the stock tires to 33's.

After reading this thread, I'm keen on getting my JK re-calibrated now. Hopefully it's not as thirsty as it seems.

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