So I just got my new Edge Evo yesterday and did all the proper updates and installed in my '03 NF-155. I'm running 315/75/16's so i reprogrammed tire size to 2760mm as per manual. Went for the test drive and my speedo is showing about 10mph faster than my GPS. Speedo and Edge showed 55mph and GPS showed only about 45mph. Because the truck is a special edition it came "factory" with 33's and the PCM was cal'd for said tires. My question is this: Would the fact that the "factory" tire size of 33" not normal small tires, be throwing off my recalibration?? Should i go to a dealer and have PCM set for actual factory tire size first? Thanks!

 

Are you sure the gears were set correctly? There is a default gear setting, and did you check to see that it was what you are running?

I would not go to the dealer. If it's not the gears etting, you have the GPS, so you know what is accurate. Just adjust the tire setting until the Edge agrees with the GPS.

 

you were correct. default gear ratio size was way off. fixed that and now i'm about 3 mph off. time to fine tune!! thanks!!

 

Good deal. Thought that might be it as you were off about 30% and that is way too much for just wheel and tire size.