If i have the dealership update my PCM with my new tire size to correct my speedo, and then program the edge for the new tire size, will it throw off the trucks speedo?

If i just update the edge will it update my trucks speedo, or will the edge say 65 and the truck say 60?

 

If you have an Edge, why have the dealer do anything? Just change your tire size in the Edge's custom menu option and then let the Edge reflash your PCM. Now both the truck speedo and the Edge will be correct. (However, the truck's speedo will read 2 mph fast when the Edge is dead on, due to some stupid design decision by Ford).

- Jack

 

oh ok, i thought that when you updated the edge, it would only update the edge MPH and not the trucks

 

The trucks PCM(computer) controls the speedometer and just about everything your truck does, such as when it accelerates, when it shifts, how firm it shifts, downshifts, everything. The tuner you have enters a new program in that computer and allows you to change many of those settings, such as tire size, gears, shift points, etc. The program you load will have a default gear setting, usually 3.73 or 3.55. Make sure when you go in to change the tire setting that the default gear setting is what your truck has for gears.