Speedometer/Odometer & bigger tires

I just put larger tires on my 2003 TJ. How do I change the speedometer to read accurately?

Reply to
Chuck Borland
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You need to get a GPS or find a 'measured mile' to find out how far off it is now.

For some reason, 33's made my CJ speedo right on and the same for 235's on my Cherokee.

You can get different gears for setting it.

Mike

86/00 CJ7 Laredo, 33x9.5 BFG Muds, 'glass nose to tail in '00 88 Cherokee 235 BFG AT's

Chuck Borland wrote:

Reply to
Mike Romain

I have a 2003 w/ 31's and it still reads about 3mph too slow according to every police radar "Your current speed is ___" setup I've driven past. Depending on your tires you may actually be right on the money.

-jd

Reply to
jdarg

Reply to
L.W.(ßill) Hughes III

There are some issues here, some websites give different speedos for the same gear and tire ratio. Also when you buy a 33" tire it is not always 33" but maybe 32.8 and then with wear it will decrease. Add to this the air pressure you put in the tire.

This is the best link so far

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But maybe the best solution is to say that you are running: this with this and the

I am sure you will get a better answer from the pros here.

I have just regeared and am playing with the same problem. I am running bfg 33 that are infact 32.8 and 4.56 gears the 36 tooth is to fast by 10km at 100km. So to correct this I need more teeth to correct the problem I just ordered a 38 tooth. I will test it with my GPS.

Reply to
Snowboardripper

The speedo gears are simply a ratio change to correct. If you are off by

10km at 100km/hour, then your speedo gear is also off by 10%. Yours is off by 10% so you need to increase the number of teeth on the gear by 10%. If you have a 36 tooth now, the closest one to fix your speedo would be a 40 tooth gear (36x1.10 = 39.6).

Chris.

Reply to
c

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JD 2K-TJ

There are some simple truths...And the dogs know what they are." Joseph Duemer

Reply to
JD

if you're gonna get that picky....don't forget that the tires expand with heat and also barometric pressure would add/subtract to the size as well!

Full tank of gas would add weight and cause the tires to balloon out....

Reply to
SB

You need to replace the gear in the Tcase where the speedometer is plugged in. There is a sensor that is spun by the output shaft, and the gear on this sensor needs to be changed.

Remove the bolt holding the sensor. Pull the sensor out. Relpace the gear. Put the sensor back in. Rotate the sensor so the gear meshes with its mate inside the tcase. Reinstall the mounting bolt.

Reply to
CRWLR

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