How accurate is the Navigation info - vehicle speed?

[Polaris Man]

I put 2” bigger tires on my truck, the Speedo and the nav info speed show the same. On my 2013 ran the nav info showed that truck was off by 3kms per hour for 1” of tire increase. Is the nav info for speed accurate? Every other number in that info part is way way off, it says distance traveled is 5 times more than I have driven, average speed 152 kms per hour etc.

 

[Wakesnowb]

You can download a speedometer app for your phone as another reference point.

 

[Conch007]

I put 2” bigger tires on my truck, the Speedo and the nav info speed show the same. On my 2013 ran the nav info showed that truck was off by 3kms per hour for 1” of tire increase. Is the nav info for speed accurate? Every other number in that info part is way way off, it says distance traveled is 5 times more than I have driven, average speed 152 kms per hour etc.

Check it on your phone you’ll see it there is a difference