Speedometer calibration

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Apr 2, 2006 | 09:32 PM

MikeRizz

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From: NH

Speedometer calibration

I just put on new 285/75/16's on my X. Do I need to have the speedo calibrated ? If so, is this a dealer only thing ?

Apr 2, 2006 | 10:42 PM

RACERX7775

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From: WARRINGTON, PA

its not going to be off more than 2mph anyway. i wouldn't waste your money.

Apr 3, 2006 | 09:48 AM

Fords4Me

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When I switched to the 285s it made mine more accurate. But it now shows 63 when I'm doing 65.

Do they ever put up those "you are speeding" trailers that show your speed near you? They do by me all the time

Apr 3, 2006 | 01:53 PM

igotoneforya

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From: Sweet Home Alabama

Racer is right, it is not off enough to worry about. The dealer can do it for 40-75 depending on the dealer. Takes only a few minutes. An aftermarket programmer/tuner will also do it but they cost more (300) while providing better air/fuel mixture ratios to improve power and possibly economy. I have 35" tires and never redid the speedo, I just know how much it is off...

Apr 3, 2006 | 09:02 PM

NewXer

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From: North Texas

Quote:

Originally Posted by Fords4Me

...it now shows 63 when I'm doing 65.

Ford4Me, any idea on what the correct reading is at 75 on the speedo?

Thanks,
Larry

Apr 4, 2006 | 02:13 AM

RACERX7775

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From: WARRINGTON, PA

yeah, if it is showing 75 then you are doing about 77 mph.. its still 2 mph difference.

Apr 4, 2006 | 04:54 AM

Fords4Me

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It's off by a certain percentage. Once you find out YOUR 2 numbers you can figure it out with a calculator.

And yes it's between 72 and 73.

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Apr 5, 2006 | 05:12 AM

Fords4Me

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Definitely a percentage. Mine is 3%. My F150 was 10%, which really sucked.

Apr 5, 2006 | 02:57 PM

#10

RACERX7775

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From: WARRINGTON, PA

any change can be converted to a percentage.

Apr 6, 2006 | 05:44 AM

#11

Fords4Me

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And once you do that you can figure out when you will be setting off the nice officer's radar unit.

Jul 12, 2006 | 05:39 PM

#12

Alaskan350

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From: Sparks Nevada

Here is a link for some calculators that I use all the time. Last one on the bottom is what you are looking for.
http://www.tyres1.com/tech_calcs.html
Zach