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The speedometer reads higher then waze gps app?

jrsimon27

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Hi friends using the waze app i see that the speed shown in the app reads like 3mph lower then the speedometer in the dash is this normal?
Thanks.
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Cory S

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Not uncommon. Most all speedometers are set to read 2-4mph higher than actual speed at 60-80mph. It gets exponentially worse after that.
 

samd1351

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I'd trust the factory speedometer over the waze app. The gps in your phone, which is what waze is using to calculate your mph, is not as accurate as the actual speedometer. Cell phone gps has an accuracy of, at best 30 meters. Trust the car.
 

Cory S

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I'd trust the factory speedometer over the waze app. The gps in your phone, which is what waze is using to calculate your mph, is not as accurate as the actual speedometer. Cell phone gps has an accuracy of, at best 30 meters. Trust the car.
The car is wrong.... All of them are. GPS accuracy in 30m is 90’. A car is traveling 88’ per SECOND at 60mph. The GPS sub net refresh rate is .50-1 second.
 

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Hi friends using the waze app i see that the speed shown in the app reads like 3mph lower then the speedometer in the dash is this normal?
Thanks.
Question? Have you changed your tire at all from factory size? If you bought used have you checked that they are still factory size? Should be a sticker in driver door jam. That size is what your speedometer is set to. if you have change tire or wheel size in anyway then your speedo will be off. And it becomes more inaccurate the faster you go. If you have factory tire size on then gps on apps get your speed by an average I have set my cruise before at 60 and watched my gps app go from 58 to 63 back and forth.

I changed my tire size and so did my buddy, both our speedos were off. We did use a dedicated gps speed app and saw how far off they were for comparison. They went in with forscan changed the values for our new wheels and tires and bingo checked against gps speed again and was dead on now.

But at the end of the day we rely to much on tech. Gonna take what a third party map app says your speed is through a satellite over and average or the actual on the ground speedometer that was calibrated at the factory? Now if you are not running oem tire sizes well that is most likely the culprit.

if you check sticker and you are running a different size go to this calculator and put in oem size and what you have now and it will tell you what speed you are off. https://tiresize.com/speedometer-calibration/
 

Cory S

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A speedometer must never read less than the actual speed or show more than 110% of actual speed + 6.25mph. So, if your true speed is 40mph, your speedometer can legally read up to 50.25mph, but never less than 40mph. In other words, if it reads 50mph, you won’t be doing more than 50mph but it’s possible you might actually only be travelling at 40mph.

Car manufacturers will normally calibrate their speedometers to read ‘high’ by a certain amount in order to adhere to this law and ensure they never show less than true speed.
 
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jrsimon27

jrsimon27

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Question? Have you changed your tire at all from factory size? If you bought used have you checked that they are still factory size? Should be a sticker in driver door jam. That size is what your speedometer is set to. if you have change tire or wheel size in anyway then your speedo will be off. And it becomes more inaccurate the faster you go. If you have factory tire size on then gps on apps get your speed by an average I have set my cruise before at 60 and watched my gps app go from 58 to 63 back and forth.

I changed my tire size and so did my buddy, both our speedos were off. We did use a dedicated gps speed app and saw how far off they were for comparison. They went in with forscan changed the values for our new wheels and tires and bingo checked against gps speed again and was dead on now.

But at the end of the day we rely to much on tech. Gonna take what a third party map app says your speed is through a satellite over and average or the actual on the ground speedometer that was calibrated at the factory? Now if you are not running oem tire sizes well that is most likely the culprit.

if you check sticker and you are running a different size go to this calculator and put in oem size and what you have now and it will tell you what speed you are off. https://tiresize.com/speedometer-calibration/
Car tires are stock.
Thanks
 

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Briebee72

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You need to update your Sync 3 to the current Build version.
I may be wrong here but sync doesn't have anything to do with your speedometer. It the microsoft file system and data management software for the head unit.
 

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My Garmin GPS says I am doing 74 when the speedo says 75. The exact same thing is true with the wife's Ford Edge. That's close enough for me.
I checked my GT with a Garmin when the car and tires were new, and speedo was also only 1 MPH faster than the Garmin all the way to 100 mph. Checked it at 25, 50, 75 and 100. The Mustang is the most accurate speedo I've seen compared to other vehicles I've had.
 
 




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