Tire Size VS Odometer Accuracy

[Jeeps Luv Mud]

Hey fellow Jeepters,
I bought a new (to me) Jeep, 2001 Wrangler Sport (TJ) 4.0L, It had 31x10.50 15 tires on it.
How do I calculate the actual mileage driven? I know different packages come with different stock tires.
I've heard you can change a small plastic gear in the trans. but is there a formula to do it?
Someone else said to flash the computer with the new info., I'm not sure my 2001 has that type of chip.
Thanks for any ideas

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[Jeeps Luv Mud]

This site helped me already!
Upon posting my question several similar threads popped up one with the answer I needed!
From Lustmord in Los Angeles, Thanks

 

[C.Sco]

This being a JL forum (2018-2025 models), most of us won't have a clue how to do anything on a 2001 TJ (although I'm sure some members here incidentally own or have owned one)

I can't help you with the computer reprogramming or the small plastic gear in the trans, no clue about either of those things in a TJ. But for converting the odometer and speedometer readings is pretty easy. I use this website:

https://tiresize.com/calculator/

Click the "Tire Comparison" tab, and enter the OEM tire size, and your current tire size, and it will give you all the info you need.

2001 Wranglers came equipped with any of the following tire sizes:

• 30x9.5r15 (Sahara and Sport) = 30.0" diameter
• 205/75r15 (SE) = 27.1" diameter
• 215/75r15 (SE and Sport) = 27.7" diameter
• 225/70r16 (Sahara) = 28.4" diameter
• 225/75r15 (SE and Sport) = 28.3" diameter

Yours is a Sport trim so it was either 30.0", 28.3", or 27.7" diameter originally. Hard to say which one without seeing the original build sheet / window sticker. Your current tires are 31" diameter.

 

[Jeeps Luv Mud]

Thanks, I am new here and hunted on the site for a place to asked about
tires and this was the thread area that came up. Thanks again

 

[roaniecowpony]

Thanks, I am new here and hunted on the site for a place to asked about
tires and this was the thread area that came up. Thanks again

There are other multi-model jeep forums and even a TJ forum or two out there. You might get some good information on this and many other things about your TJ.

 

[Jeeps Luv Mud]

This being a JL forum (2018-2025 models), most of us won't have a clue how to do anything on a 2001 TJ (although I'm sure some members here incidentally own or have owned one)

I can't help you with the computer reprogramming or the small plastic gear in the trans, no clue about either of those things in a TJ. But for converting the odometer and speedometer readings is pretty easy. I use this website:

https://tiresize.com/calculator/

Click the "Tire Comparison" tab, and enter the OEM tire size, and your current tire size, and it will give you all the info you need.

Thanks,
Does the site have a TJ area?
If it does, I haven't found it yet.

 

[Jeeps Luv Mud]

There are other multi-model jeep forums and even a TJ forum or two out there. You might get some good information on this and many other things about your TJ.

Thanks Man, when I signed up here I thought it was a multi-Jeep forum.
Keep on Jeep'in

 

[C.Sco]

Thanks,
Does the site have a TJ area?
If it does, I haven't found it yet.

No this is pretty much just a JL forum. check out https://wranglertjforum.com/
Also check out my post above again, I just added some edits with more info

 

[Jeffy56]

Old school. Yes there are different gears for the speedo cable output. You'd have to research that particular Jeep model transmission. Amazon/Autozone/O'Reilly's should have a "set".
Calculate real speed by time to do one mile @ 60 MPH or a phone GPS with options program. Calculate error % vs number of gear teeth. Change and re-check. I use "GPS test" phone app.

https://play.google.com/store/apps/details?id=com.chartcross.gpstest&hl=en-US

Fun when flying. Doesn't need a data connection.

 

[Jeeps Luv Mud]

Cool Thanks again

 

[Jeeps Luv Mud]

No this is pretty much just a JL forum. check out https://wranglertjforum.com/
Also check out my post above again, I just added some edits with more info

Cool Thanks again

 

[Jeeps Luv Mud]

Old school. Yes there are different gears for the speedo cable output. You'd have to research that particular Jeep model transmission. Amazon/Autozone/O'Reilly's should have a "set".
Calculate real speed by time to do one mile @ 60 MPH or a phone GPS with options program. Calculate error % vs number of gear teeth. Change and re-check. I use "GPS test" phone app.

https://play.google.com/store/apps/details?id=com.chartcross.gpstest&hl=en-US

Fun when flying. Doesn't need a data connection.

For you guys not being a TJ site I got lots of help anyway

 

[LukeDagny]

I can't find the chart I used with my TJ, but the gearing is dependrent on tire size (obviously) a on transmission.

I used this forum for my TJ

https://wranglertjforum.com/

 

[Jeeps Luv Mud]

I can't find the chart I used with my TJ, but the gearing is dependrent on tire size (obviously) a on transmission.

I used this forum for my TJ

https://wranglertjforum.com/

I'll check it out

 

[roaniecowpony]

Old school. Yes there are different gears for the speedo cable output. You'd have to research that particular Jeep model transmission. Amazon/Autozone/O'Reilly's should have a "set".
Calculate real speed by time to do one mile @ 60 MPH or a phone GPS with options program. Calculate error % vs number of gear teeth. Change and re-check. I use "GPS test" phone app.

https://play.google.com/store/apps/details?id=com.chartcross.gpstest&hl=en-US

Fun when flying. Doesn't need a data connection.

I used a GPS app to validate the tire size recal on JSCAN. Worked great on a straight stretch of hwy.

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