tire size affecting mpg??
Rookie
Joined: Jan 2007
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RE: tire size affecting mpg??
ORIGINAL: moparrtguy
I was just thinking about this today. Since I put my lift and 35" tires on the truck, my gas milage has been horrible. I used to get about 12 mpg in the city now I am only getting 7 mpg!!!! I can only go about 200 miles on a tank of gas. I am running 3.55 gears right now and plan to re-gear lower - but I would like to have my speedo accurate as well. My milage may not be as bad as I think it is because the tire size is messing up the accuracy of the odometer. My question is, where can you get the speedo re-callibrated? Can a Dodge dealership or local repair shop do this?
I was just thinking about this today. Since I put my lift and 35" tires on the truck, my gas milage has been horrible. I used to get about 12 mpg in the city now I am only getting 7 mpg!!!! I can only go about 200 miles on a tank of gas. I am running 3.55 gears right now and plan to re-gear lower - but I would like to have my speedo accurate as well. My milage may not be as bad as I think it is because the tire size is messing up the accuracy of the odometer. My question is, where can you get the speedo re-callibrated? Can a Dodge dealership or local repair shop do this?
Veteran
Joined: Apr 2006
Posts: 464
Likes: 0
From: Yuma, Az.
RE: tire size affecting mpg??
I have the same question as moparrtguy. When I asked the dealer about putting the 3rd gen 20's on my truck, they freaked out and said ABSOLUTELY NOT. So I did it anyway after bringing the question up on here. So with that I really don't want to go to the dealer and listen to there BS!
Veteran
Joined: Dec 2005
Posts: 267
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From: Peoria, Az
RE: tire size affecting mpg??
Well I really didnt want to spend $300 on a programmer just to re-callibrate the speedo. I am due for an oil change so I will check into the dealer callibrating it. I know they are going to charge me an arm and a leg since they charged me $94 just to flash my Mopar Performance PCM.
All Star
Joined: Mar 2006
Posts: 904
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From:
RE: tire size affecting mpg??
I am buying new 285's in the spring. I want Mud tires, but I doubt that the tread life will last long on the streets. But I don't like all terrains, its not aggressive enough. You guys got any aggressive 285's that you know about
Champion
Joined: Aug 2005
Posts: 3,313
Likes: 8
RE: tire size affecting mpg??
here's an old post that has valuable info on the proper way for a tech at a Dodge dealership to re-calibrate the speedo. Most techs don't know this detail and may tell you they can't recalibrate for your tire size. Print this out and take it with you to the dealership:
---
originally posted by grfraz
Augusta GA
Here is the recipe.
1) Have the tech plug his hand held into the OBD port and turn it on. A menu
screen comes up with a bunch of info. Select YES to go to next screen.
2) On this screen select menu item 1, "DRB III Standalone" to go to next screen.
3) On this screen select menu item 1, "1998-2005" to go to next screen.
4) On this screen select menu item 1, "All" to go to next screen.
5) On this screen select menu item 5, "Antilock Brakes" to go to next screen.
6) On this screen select menu item 9, "Miscellaneous" to go to next screen.
7) On this screen select menu item 2, "Set Pinion Factor" to go to next screen.
8) On this screen there are a several tire sizes and Other. Select menu item 8,
"Other" to go to next screen.
9) On this screen there are two items, an Axle Size, (9.25" on the 1500's and
10.5" on the 25/3500's) and Other. Select menu item 1, "9.25" Axle" (10.5 in
your case) to go to next screen.
10) You have now arrived at the point in this process where you will enter the
revolutions per mile for your tire size. Select the menu box for RPM. It will
indicate 400. Here is where the tech will change the revs per mile with either
the up or down arrow. It will take a while to go from 400 to 604 (for the BFG
315's) so be patient. As you are waiting on him to finish, take this time to let
him know that he shouldn't charge you more than say $20.00, especially since you
trained him on this procedure.
11) The last step is to select "OK" and the changes will be excepted, then the
hand held will display "Reprogramming Successful".
Good luck!
======
There is an online Java calculator to compute revolutions per mile at:
http://pw1.netcom.com/~sgalaba/tiresize.htm
---
originally posted by grfraz
Augusta GA
Here is the recipe.
1) Have the tech plug his hand held into the OBD port and turn it on. A menu
screen comes up with a bunch of info. Select YES to go to next screen.
2) On this screen select menu item 1, "DRB III Standalone" to go to next screen.
3) On this screen select menu item 1, "1998-2005" to go to next screen.
4) On this screen select menu item 1, "All" to go to next screen.
5) On this screen select menu item 5, "Antilock Brakes" to go to next screen.
6) On this screen select menu item 9, "Miscellaneous" to go to next screen.
7) On this screen select menu item 2, "Set Pinion Factor" to go to next screen.
8) On this screen there are a several tire sizes and Other. Select menu item 8,
"Other" to go to next screen.
9) On this screen there are two items, an Axle Size, (9.25" on the 1500's and
10.5" on the 25/3500's) and Other. Select menu item 1, "9.25" Axle" (10.5 in
your case) to go to next screen.
10) You have now arrived at the point in this process where you will enter the
revolutions per mile for your tire size. Select the menu box for RPM. It will
indicate 400. Here is where the tech will change the revs per mile with either
the up or down arrow. It will take a while to go from 400 to 604 (for the BFG
315's) so be patient. As you are waiting on him to finish, take this time to let
him know that he shouldn't charge you more than say $20.00, especially since you
trained him on this procedure.
11) The last step is to select "OK" and the changes will be excepted, then the
hand held will display "Reprogramming Successful".
Good luck!
======
There is an online Java calculator to compute revolutions per mile at:
http://pw1.netcom.com/~sgalaba/tiresize.htm
