Hey guys just put a set of 290/70/17s on and adjusted my edge to lik 2552mm. I'm seeing a 2 or 3 mph difference in my edge speed and my needle. is this normal or have i done something wrong?

 

The truck speedometer is always 2-3 mph fast. Ford builds them that way.

 

Kinda what I was thinking just wanted to Kick the idea around!! THANKS

 

Really? My Gryphon speedo, dash speedo, and GPS speedo are all almost exactly the same. Off by less then 1 mph. Weird.

 

Occasionally we hear of one, but nearly all are off about 2 mph at 60 to 65 mph. I never look at the truck speedo anymore, just the digital monitor which is right on with a GPS.

 

is the mileage calculation on the trip computer and odo correct though?

 

Same with mine. GPS and Edge are exactly the same where as the truck is 2-3mph fast.

 

Yes - If you adjust the Tire Size so that the Edge/Gryphon speed readout is accurate, then the truck's ODO will also be accurate, even though the speedo needle MAY be about 2-3 mph fast at 75mph. The discrepancy here is the result of translating a digital signal to drive an analog display for speed. But the ODO is all digital.

- Jack