Larger tire = odometer off?
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New User
Joined: Mar 2010
Posts: 20
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From: Hwy 41 in Central Cal
Larger tire = odometer off?
I recently replaced my stock tires 255/65-17 with 265/70-17 on my 2004 F150 4x2.
With the original tires the speedometer was reading 3 mph too high (according to my gps) and as far as I know the odometer was correct.
Since putting on the larger tires, my speedometer is now right on money (per my gps) but it seems as though my odometer is off (haven't done a 1 mile marker to marker measurement yet)
Are the speedometer and odometer directly linked in these new electronic vehicles or can one be correct and the other be off?
Any insight would be greatly appreciated.
Thanks
With the original tires the speedometer was reading 3 mph too high (according to my gps) and as far as I know the odometer was correct.
Since putting on the larger tires, my speedometer is now right on money (per my gps) but it seems as though my odometer is off (haven't done a 1 mile marker to marker measurement yet)
Are the speedometer and odometer directly linked in these new electronic vehicles or can one be correct and the other be off?
Any insight would be greatly appreciated.
Thanks
Freshman User
Joined: Jan 2010
Posts: 38
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From: Port Coquitlam, BC
The never trucks have no speedo cable so It should be dead on almost as the older trucks did have a speedo cable and you had to calibrate. It could be something wrong with the computer which controls the speed because no matter the size of the tires the computer is supposed to calibrate.
Hotshot
Joined: Oct 2002
Posts: 18,488
Likes: 22
From: The Big, Oregon
There is no way the computer can automatically compensate for the tires, it doesn't know. All the speedometer is is a tachometer for the driveshaft (or a wheel speed sensor on newer trucks), calibrated to read in miles per hour. The odometer converts the revolutions into an accumulated distance based on it's calculation of distance traveled per revolution. You will travel further on larger tires, but the speedometer and odometer will still display the info for the smaller tires.
You can have it reprogrammed to compensate for the larger tires.
You can have it reprogrammed to compensate for the larger tires.
Freshman User
Joined: Oct 2010
Posts: 26
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From: SW Virginia
Yea, I just got my 99 speedo reprogrammed - all I had to give the guy putting the tune on the engine was the revolutions per mile of the new tires (inches in mile divided by tire circumference-plenty of calculators online) and he fixed me right up. Dead on.
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