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Old 12-03-2012, 12:07 PM   #1
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How to calculate odometer for 33s

I was wondering my mpg I have 33s with 3.73 but never geared the odometer how do you calculate how many miles you've gone this way. I know the odometer goes up slower I also want to know for oil changes and all

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Old 12-03-2012, 12:17 PM   #2
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You could get a new speedo gear and not have to calculate anything or use a smart phone with a gps based speedo applicaton on it and see how far off (percentage) your speedo is from the GPS app. Us that same percentage to correct your odometer. Really though, just get a new speedo gear, its 5 min to change.

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Old 12-03-2012, 12:19 PM   #3
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Quote:
Originally Posted by kpla51
I was wondering my mpg I have 33s with 3.73 but never geared the odometer how do you calculate how many miles you've gone this way. I know the odometer goes up slower I also want to know for oil changes and all
I would check with a GPS to see how far you speedo is off currently and if you know about what miles was on it when you put the 33' on you can figure it out roughly. I'm in the same boat but don't know when the 33's where put on initially. I just add 10% to the current miles. Lol
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Old 12-03-2012, 12:24 PM   #4
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It is sort of a moot point to convert to actual miles covered. Maintenance based on miles traved is not an exact science. It is a general rule of thumb that the drivetrain has rotated a certain amount and the fluids should now be changed. Obviously the rotations can vary greatly between vehicle brand/model/physical configuration. With the larger tires, your mechanicals are turning less, so don't stress that you actual miles traveled may be over the magic number for fluid change.

With that said, it is very easy to change your speedometer gear
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Old 12-03-2012, 12:24 PM   #5
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A simple way to get a better MPG figure is to just determine (by %) how much bigger the 33's is over the tire the Jeep came stock with. Add that % back in to your MPG.

You can allow measure the circumference/rollout % difference between stock and the 33's and add that % back in.
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Old 12-03-2012, 12:25 PM   #6
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Your speedo is 14.99% slower, so add 14.99% to your mileage

http://www.1010tires.com/tiresizecal...?action=submit
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Old 12-03-2012, 12:26 PM   #7
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what gear should i buy any links?
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Old 12-03-2012, 12:28 PM   #8
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I have 33" tires 17" wheels. By multiplying 1.18 x odometer I get the true mileage. Per my GPS
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Old 12-03-2012, 12:28 PM   #9
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Old 12-03-2012, 12:33 PM   #10
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Originally Posted by Renegade44 View Post
I have 33" tires 17" wheels. By multiplying 1.18 x odometer I get the true mileage. Per my GPS
So I believe that shows that your tires 18% bigger than the tires the Jeep came stock with.
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Old 12-03-2012, 12:43 PM   #11
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I found out that the spedo charts were off. With my set up (33's and 4.10's) I read 34 tooth was what I needed, I was still off by 6 MPH, so I returned that and went with 35 tooth and I am 100% spot on with milage and speed. (I know I know its only 6 mph but I am anal. If it ain't right it bothers me...

I used a GPS to determine what gear I needed and told the folks at 4Wheeldrive in Raleigh what my speedo said and what GPS said and they said yep you need the 35.

It truely takes 5 minutes to swap out (well 10 for me, cause I had to do it twice)
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Old 12-03-2012, 12:51 PM   #12
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Yea you have to get the speedo gear for the actual size of your tire not the advertised size...

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