1985xjlaredo
NAXJA Forum User
- Location
- Kansas City
Anyone know how do to a roll back? I dont wanna cheat anything just want to get close to the actual miles, My tires have thrown it way off. There is no way I drove 8000 miles in the last 6 months.
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Odometer Roll Back
- Thread starter 1985xjlaredo
- Start date
FELIX
Who Knows, Ask Who
- Location
- Camarillo, CA
I don't think your going to get an answer, as this is an illegal and fraudulent practice:nono: . Oh and by the way, if you know what to look for, you can usually figure out it has been done. Why don't you get the correct spedo gear and correct the problem :conceited
Rob $.02
Rob $.02
JNickel101
NAXJA Forum User
- Location
- Alamogordo, NM
No, bigger tires make it look like you are going faster and therefore more distance....
- Location
- Coshocton, OH
Maybe to the cop that pulls you over cause your speedo said you where going 60 and his radar said it looked like you where going 73.JNickel101 said:
Bigger tires will make your speedo read slower.
JNickel101
NAXJA Forum User
- Location
- Alamogordo, NM
Explain how my buddy's TJ with 35s and 4.88 gears pins his speedo at 100MPH as we're going down the highway....
JNickel101
NAXJA Forum User
- Location
- Alamogordo, NM
And I assure you, we're not going nearly that fast....
SuperRA
NAXJA Forum User
- Location
- Santa Clara, CA
I changed out the cluster on my pickup for one with a tach and waited until my mileage was the same as the new cluster. Then I took a picture of both of them showing the same miles. Probably didn't have to do all that but I did anyways.
And also, smaller tires will make your speedo read faster and farther than you are actually going and visa versa. A speedo simply counts the number of revolutions per given amount of time. A smaller tire will cover less distance per revolution than a bigger tire thus lesser revolutions for the bigger tire.
Because your rear gears are overpowering the effect of bigger tires. Try this calculator.
http://www.angelfire.com/fl/procrastination/rear.html
I put in 3000 RPM (typical freeway RPM), 35in tire, 4.88 gear, 0.8 transmission gear (assuming OD, not sure of exact ratio) and got approximately 80mph
That's what you are probably actually travelling at.
And also, smaller tires will make your speedo read faster and farther than you are actually going and visa versa. A speedo simply counts the number of revolutions per given amount of time. A smaller tire will cover less distance per revolution than a bigger tire thus lesser revolutions for the bigger tire.
JNickel101 said:
Because your rear gears are overpowering the effect of bigger tires. Try this calculator.
http://www.angelfire.com/fl/procrastination/rear.html
I put in 3000 RPM (typical freeway RPM), 35in tire, 4.88 gear, 0.8 transmission gear (assuming OD, not sure of exact ratio) and got approximately 80mph
That's what you are probably actually travelling at.
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1985xjlaredo
NAXJA Forum User
- Location
- Kansas City
Yea the PO that owned my Jeep before me had 245/55/15 tires on it for at least 50,000 miles. Maybe I did drive that much in the last 6 months lol Stock size is what I have on now. it still seems to be racking up miles really fast though.
1985xjlaredo
NAXJA Forum User
- Location
- Kansas City
good point bfred.
Y wouldn't I get an awnser? And well I dont know what to look for or else I would not have asked:looser:
FELIX
Who Knows, Ask Who
- Location
- Camarillo, CA
1985xjlaredo said:
You miss understood, I meant you can usually tell if it has been done, not you knowing how to do it. And awnser is spelled answer.
Rob
Blaine B.
NAXJA Forum User
- Location
- Northwest Indiana
Disconnect the speedo gear harness and drive another 8000 miles.
I would, but there's not enough information to answer specifically.JNickel101 said:
I will however make some assumptions.
It's likely that he had 3.07 gears from the factory, so 3.07's and stock sized 225 tires.
Now, put 4.88's in there and go to 35s.
Did he change the speedometer gear, because now your tailshaft is spinning faster.
There's not a magical speed sensing GPS chip in there, it's mechanical. So unless you change out the gear in the tailshaft your speedometer is wrong.
just like mine, I can bury it to 90 when I'm only going 75. it's a linear ratio.
and basic geometry tells you that a larger tire travels a greater linear distance per revolution, try geometry 101, specifically circumference. It's a pretty cool thing to understand basic math.
yes, I was mean, but don't come on here and spew forth blatantly wrong information and then argue about it.
that just makes you a tard.
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Blaine B.
NAXJA Forum User
- Location
- Northwest Indiana
Eww maths.
MentalBill
NAXJA Forum User
- Location
- Hawaii
OK maybe I am just throwing gas on the fire BUT!
I have used this http://www.1010tires.com/TireSizeCalculator.asp (there are others) to figure out how much off my speedo was when getting different sized tires. It doesn't help with gears thou.
To "roll" back a odo. I have never done it, but I was told by my dad that back in the day they would hook up a drill to the speedo cable and run it back. Or maybe it was forward. I don't remeber. Anyway I like the Idea of driving 8000 miles with it unhooked.
mentalbill
I have used this http://www.1010tires.com/TireSizeCalculator.asp (there are others) to figure out how much off my speedo was when getting different sized tires. It doesn't help with gears thou.
To "roll" back a odo. I have never done it, but I was told by my dad that back in the day they would hook up a drill to the speedo cable and run it back. Or maybe it was forward. I don't remeber. Anyway I like the Idea of driving 8000 miles with it unhooked.
mentalbill
Blaine B.
NAXJA Forum User
- Location
- Northwest Indiana
LOL but you won't see yer speed either! 
The speedometers now are electronic (right?) meaning there's a wire leading from the speedo gear to the dash. However I wonder if spinning the speedo gear quickly with a drill with the ignition on would have the same effect as spinning the mechanical speedometer cable back in the day
FBI just stopped infront of my house....bye!
The speedometers now are electronic (right?) meaning there's a wire leading from the speedo gear to the dash. However I wonder if spinning the speedo gear quickly with a drill with the ignition on would have the same effect as spinning the mechanical speedometer cable back in the day
FBI just stopped infront of my house....bye!
They don't roll backwards...haven't any of you guys seen "Risky Business" Just ask Tom Cruise...Blaine B. said:LOL but you won't see yer speed either!
The speedometers now are electronic (right?) meaning there's a wire leading from the speedo gear to the dash. However I wonder if spinning the speedo gear quickly with a drill with the ignition on would have the same effect as spinning the mechanical speedometer cable back in the day
FBI just stopped infront of my house....bye!
RickyN29
NAXJA Forum User
- Location
- San Jose, California
First off, larger tires will show a slower speed than actual travel (and hence less miles than actually accumulated). So if anything, you need to ADD mileage to the rig, not subtract.
As for changing the mileage, it is actually quite easy on the mechanical odometers. A couple buddies did cluster swaps and wanted to match the mileage. I took their mileage and the new clusters and simply set all the dials to match. Take it apart, it was REALLY easy.
However, changing the mileage to reflect less mileage than actually on the vehicle is low. Be proud of your travels.
As for changing the mileage, it is actually quite easy on the mechanical odometers. A couple buddies did cluster swaps and wanted to match the mileage. I took their mileage and the new clusters and simply set all the dials to match. Take it apart, it was REALLY easy.
However, changing the mileage to reflect less mileage than actually on the vehicle is low. Be proud of your travels.
Anywho its only illegal if you are trying to sell the rig with lower mileage. Ive done this on a couple of my drag cars to keep records of the amount of miles put on them. Its quite easy. Take out bezel and pull off the plastic. Just look around you will figure it out. Just dont tear it all the way apart or you will be looking for a new cluster.
