Speedometer displays slower than car

[Lonewolf147]

Try your Drive A Mile test again. Divot based on mile markers in a different location.

OK, I'll try it again in a few different locations.

Thanks everyone else for the input.

[OldGnome]

Car speedometers generally read high to keep you out of trouble.

This matches my experience exactly. I drive many different cars (I travel a lot for business) and have used a Garmin and now Waze. Whenever I have passed a "you are going this fast" sign, the speed on the Garmin/Waze matches very accurately to the sign. I have also done a driving test and the Garmin/Waze are more accurate than the speedometer.

Some vehicles (especially those with a digital speed readout) have more accurate speedometers than others.

YMMV

[rbthomp76]

I use Waze on an iPhone 4S. I also have a Garmin that run as well (guidance is pretty well covered). I have noticed that the speed on Waze (and thus the iPhone) is behind when starting and stopping. Once I get to a set speed, both the iPhone and the Garmin agree. My speedometer doesn't but that is a tire thing.

So, I think the GPS units in phones don't update as quickly as a stand alone GPS unit. But then against that is just a guess on my part based on what I've seen.

Perhaps that is what your seeing.


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[Sahirsiddiqui]

My experience is that both Waze (& my old Garmin GPS) show speeds almost exactly 10km/hr slower than my actual speed.

[simonhowes]

My little Mazda MX5 Miata and two Ford Focus speedo shows 70mph but Waze and my Garmin satnav show 63-65mph. I have tried holding an anemometer out of the window and Waze was correct. Cars are normally given -10% tolerance at max, also switching wheels and tires to different sizes can have an effect if the circumference is different. My friends Range Rover and Audi R8 match Waze perfectly.

iOS isn't accurate. You can only poll for a location once every 15 seconds plus it also use AGPS, DGPS would be the best way to get accurate readings.

[xteejx]

Also, speedometers are 10% too fast by design. This includes digital displays.

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