Nav. MPH vs Speedometer

novelmike · Nov 29, 2015

So I recently put bigger tires on my 2012 Ram 1500. They measure about 2" taller. I expected my speedometer to be off 1 or 2mph at 80mph. But it still reads exactly what my factory navigation speed says I'm going. Are these 2 linked together so they always read the same speed?

Hootbro · Nov 29, 2015

Would not surprise me if they are linked. I know many if not most factory NAV systems have a Vehicle Speed Sensor (VSS) input into them from the vehicle so they track the same.

I would suspect it is a CAN BUS input on these trucks and not a dedicated feed wire.

MoreOvalteenPlz · Nov 29, 2015

Must be nice to have NAV! I upgraded to 1" taller Cooper Discoverer S/T Maxx's and my speedo is off roughly 2 mph at 70 (set cruise to 68 when really going 70).

CuylerTech · Nov 29, 2015

on the 2013+ the speed Nav reads is not from the vehicle, but from the sat. I know because my 2.5" taller tires give me 3-4MPH off what im going, but the GPS is always 3-4MPH higher then the actual speedo.

novelmike · Dec 1, 2015

Ok, thanks for your help guys. I'm now on the lookout for a car that has the digital speedometer so I can compare speed readings while on the freeway haha! Now if I can only find a freeway in Orange/L.A. county that I can drive 70mph......

Tim7139 · Dec 5, 2015

Most phone GPS sensors are decent, and there are lost of free and low cost app options.

Nav. MPH vs Speedometer

novelmike

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Hootbro

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MoreOvalteenPlz

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CuylerTech

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novelmike

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Tim7139

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