So I just installed my 35x12.50x17 BFG KM2's and I went to recalibrate my speedometer and when I check it against my AVIC-Z2 it's off by 7mph at 70. My speedo and edge say 63 and my GPS says 70, so 10% error. I've tried multiple settings and none do anything. I have even set it up to like 3000mm and it still reads under. Am I doing it correctly?

 

Have you verified that your gear ratio is correct? Both the tire size and gear ratio can be "bogus" values when you are setting the "custom options". If the gear ratio is correct, all I could suggest is move the tire circumference up to 3300 mm. (I know, this "fix" seems wrong too).

- Jack

 

The thing is, I tried 2500, 2600, 2800, then 3000 and it doesn't seem like any of them change anytihng.

 

And, did you verify that your gear ratio is correct? It CAN be something totally wrong.

- Jack

 

I guess I didn't check this time, it just has always been correct when I did custom tunes, unless I got a different ratio from the factory than I was told. I have 3.73s.

 

Like Jack said, check the gear ratio. Also make sure you are saving your changes, not backing out with the menu button. You said none of the settings seem to make a difference so it sounds like you either aren't saving your changes or you are doing it correctly and the programmer isn't saving them.

 

Ray may have hit on it! Thanks, Ray! I can overlook the obvious so often! :o

- Jack

 

I'm not taking any credit unless that turns out to be the problem Jack. It is easy to overlook the easy stuff (don't ask me how I know) so that's usually the best place to start. It's been awhile since I've messed with the the tire settings in my Edge but I think the save procedure is different than some of the other functions which can be a little confusing.

 

sorry to hijack, but when you recalibrate on the edge, does it change the speedo reading on the cluster?

 

Yes - it does. Both the Edge and the dashboard speedometers get their input electrically from the PCM. When you change the tire size in the Edge and program the PCM with that, it sends correct information to the speedo, and the odometer.

It's been noted though, in several posts, that if your Edge speed is dead accurate, the dashboard speed will be about 2 mph faster in the 70 mph range. The odometer will be accurate here though. Why is the dash speedo fast? Because Ford designed it that way.

- Jack

 

thanks for the reply, I appreciate it. Cant wait to get a gryphon

 

Did you ever get this corrected? Was it because you weren't saving the settings?