how much is your speedo off
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From: herriman utah
how much is your speedo off
I am running bone stock tires and wheels, and my speedo appears to be about 2.5mph fast. wonder if this is done on purpose to make people think they are getting a little better mileage than what they really are.
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Joined: Jul 2010
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From: Salt Lake City, UT
I didn't check mine until after I put larger tires on (35's). I checked it w/ a gps a few weeks ago and it was dead on at multiple speeds. I checked 10, 25, 50, etc. So it must have been off before the new tires.
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From: herriman utah
one thing to keep in mind 2 or 3mph is going to make a big difference when your speeds approach 75-80mph, I bet its going to be about 5% difference in fuel economy. I am wondering if ford did this on purpose.
or since my truck came with the plain jane might as well be work truck wheels they are 17" I think the 18" wheels are a bigger tire or more correctly a slightly taller tire, maybe they just use one calibration and it suits the taller 18" OEM tires better.
or since my truck came with the plain jane might as well be work truck wheels they are 17" I think the 18" wheels are a bigger tire or more correctly a slightly taller tire, maybe they just use one calibration and it suits the taller 18" OEM tires better.
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If that were the case, why do my even taller 20s still read slightly fast on the speedometer? The answer to your question is the PCM contains information on both the gear ratio and the tires rev per mile. My finding on the 05-07 was that the revs per mile that they program into the PCM is slightly conservative.
I can't explain to you how the speedo could be off in one direction and the odometer off in a different direction other than we are not dealing with two mechanically linked items as they once were. All I can tell you is that my speedo reads about 2.5 mph fast and my odometer reads about 3.5% low. This would actually make my fuel economy better not worse. I also am far from the only person that has reported virtually the same observations.
I can't explain to you how the speedo could be off in one direction and the odometer off in a different direction other than we are not dealing with two mechanically linked items as they once were. All I can tell you is that my speedo reads about 2.5 mph fast and my odometer reads about 3.5% low. This would actually make my fuel economy better not worse. I also am far from the only person that has reported virtually the same observations.
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the speedo/odo can be recalibrated for each OEM tire size, and for aftermarket sizes. It makes sense that the deviation is similar on different size tires.
Mine reads about 1-2mph high (as compared to my GPS) at 60 mph. I also checked by mile markers, and the indicated distance traveled is about 4% lower than actual. This seems to be about average for most OEMs. I'm not complaining... It means that I'm actually getting better mpg than I thought, and my warranty will last about 4% longer than I thought
Mine reads about 1-2mph high (as compared to my GPS) at 60 mph. I also checked by mile markers, and the indicated distance traveled is about 4% lower than actual. This seems to be about average for most OEMs. I'm not complaining... It means that I'm actually getting better mpg than I thought, and my warranty will last about 4% longer than I thought
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