Speedometer help

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Mar 18, 2013 | 09:08 PM

PSD2005

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From: FLORIDA

Speedometer help

My Gps says 68 and my speedometer 71! I have a programer to change it, do I need to move the tire size up or down to get the two right!! Thanks

Mar 18, 2013 | 10:19 PM

donniezyea

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From: Saukville WI

Kinda wondering myself why mines like that, the edge cts insight has that corrected speed on it but really what is the deal with the speedo being off? ^Hope someone helps

Mar 18, 2013 | 10:22 PM

bpounds

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From: Whittier, CA

That's exactly how Ford programs them from the factory. About 3MPH too high at highway speeds. My advice is to just live with it. Such a small error isn't worth worrying about.

Mar 18, 2013 | 10:24 PM

Yahiko

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From: Spanaway

You may find this tool useful on the RPM of the tire per mile.
Tire Calculator
With this info you can find the right # to make the correction.

Sean

Mar 18, 2013 | 10:26 PM

Bullitt390

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Most speedometers are calibrated to read a little faster, especially motorcycles. It's by design.

Josh

Mar 18, 2013 | 10:38 PM

donniezyea

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From: Saukville WI

Quote:

Originally Posted by bpounds

That's exactly how Ford programs them from the factory. About 3MPH too high at highway speeds. My advice is to just live with it. Such a small error isn't worth worrying about.

This is news to me wow-answered my question thanks!

PSD2005 3mph off isn't too bad my 91 f-150 has 33's its like 8mph off - dosent bother me

Mar 18, 2013 | 10:50 PM

bpounds

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From: Whittier, CA

Yeah, lots of theories about why the do that. Some think it is Ford cheating owners on the warranty period. Maybe. I think they just want the error to be toward the slow side, so they don't get sued every time someone gets a speeding ticket.

I went from stock 31.5" tires to 33" ties, and now my speedo is about 3mph off in the other direction. It's still close enough to not be an issue.

Before the wonderment of GPS, we would have never known such a minor error existed.