So if your speedo needs correction when you install larger tires, what about your ODO? Does anybody have an equation on how to figure out the correct mileage for your truck?

T.I.A

 

I would think it would, but I don't know if it would really be enough to matter. A programmer is an awesome way to correct this if you have the $$$.

 

I'm pretty sure you can take it to the dealership and they can fix it. I think it costs around 50bucks.

For some extra money just by a programmer and do it yourself.

Mine is off a little but I have driven by the radar signs with the GPS and figured that my speedo was about 2mph over what I'm actually going with the larger tires.

 

Ya I have been wondering the samething. My speedo is 3 to 4 mph slow with my 33's and the same with stock. So am I really putting less miles on then what Im really doing?

 

thats my point....service for oils,fluids are very important to me...I do own a programmer but how would that fix the Odometer?

 

on the edge you have to figure out the circumference of your tire. if you have the manual it lists a few common sizes and also gives a formula to determine it. assuming that you still have 325/60r18 (as it says in your sig), your circumference is 2660. so now you need to go to power programming and choose which level you want and when it asks to "create a custom program?", choose yes and then enter your gear ratio and tire circumference. that will correct your speedo and odo.

 

I would think the odometer and speedometer use the same pulse signal to generate their output, so you can't change them independently (unless you're an electrical genius and can futz with the electrical components inside them).

The chances of them matching exactly are pretty slim too, so you'd want to correct for the odometer and let the speedo fall where it may.

 

bigchief2472000,
I do have it configured on my Edge, but the Speedo gauge is still off...which would mean the ODO is off. I guess I just have to figure an algorithm for the difference of speedo to find the variable for actual mileage.

 

Oh I get it now, it took me a min/day to understand this. So your saying that after all of this time of the speedo being off then the odometer would in turn be off by a few hundred miles? I don't know that there would be anyway to correct it because isn't it illegal to mess with the odometers on vehicles? I mean it's not like you could ask them to spin it back a couple hundred miles.

 

only a few hundred even after putting 85k on the clock with larger than stock tires? I wonder if Ford compensated for the change in rim and tire package that comes with the FX4 by programming the correct rotation travel for the tires? Say PCM tune differently?

 

A few thousand? is that better? lol...

 

How much are you off and which direction? By that I mean is your speedo. reading fast or slow? I'm sure the odometer is off by the same amount. If your speedometer is reading 2 mph slower than actual and you drove 70 mph for 1 hour you actualy covered 72 miles. 2 divided by 72 equals 2.8%. So for every 1000 miles you have actualy put on 1028 miles. But because your tires are bigger, your drivetrain etc. really only put on 1000 miles.