I just got my whole truck done, 35's on 20's pro comp 6inch, 456 gears, and edge. I am running level 2 custom w/ the adjustments for my gears and the tires. I have 325/60-20 nitto's and i calculated that out to 2821mm. Now inputing all that should make my speedo be correct again right?? but i feel like it is still way way off at high speeds and just 3 or 4 mph off at low speeds.

 

Please see your own thread you started before. Your speedometer will be off, no matter what you do.

https://www.f150online.com/forums/sh...d.php?t=248272

 

You can only realisticaly calibrate your speedo up to a certain size, I don't know what the limit is, but with those size tires I would say you probably have surpassed it. Like I said, I don't know for certain, but that would be my guess.

 

I did read my own old thread and i appreciated the info and understood it all. What i was asking in this thread is if other people that are running custom edge programs have a noticable difference between what their display's are reading be it either edge or factory gauge, and the speed they are actually doing. I understand that there will be a slight difference btwn the edge and the factory speedo,, but i want to know does the edge program actually correct for the larger tires like it says it does and i have something programed incorrectly or does everyone w/ 35's or larger have the same problem. I mean around 40 or so i feel its only 2 or 3mph off,,, but when it says i am going 70mph there is no way i feel like im doing like 50mph

 

I took out my GPS and started playing with the numbers. According to Edge my 325/60/18's are something like 2660mm. If I put that number into the unit at 60 mph I am off by 3.5 mph, which is the same that my speedo was off from the factory when the truck was bone stock. So now ofter playing with the numbers alittle bit I have the stock speedo reading the same as the GPS. To do this I ended up having to put 2510mm in as the dia. of the tires. I am sure that my odometer is off a little bit, but big deal. I would rather have the speedo correct.

 

Just look in the manual that came with the Edge. They have the calculations already done and you just program the Edge to make it almost correct. It may be a little off but my truck seems to be pretty close to correct.

 

So I just had a very devious thought. If you could adjust the diameter of the tires to affect the speedo and the mileage, could you adjust it to show real low mileage even though you drove alot. Now before you flame on how immoral that is, you could do it right........? That maybe something someone needs to be aware of (if it worked) when buying a used 04 to 06 down the road.

 

If it "could" be done, your speedo would be so far off that it would be very hard to put alot of miles on, IMO. But I am not sure how far the Edge will let you decrease the tire size, since I have never tired it, or will ever want to do that.
I just did this so that my speedometer would read the correct speed, not to change the accuracy of the odometer in anyway. That just happen to be one bad side affect of it.

 

okay so i grabbed 2 of my buds today and went for a ride. One had gps on his phone, the other had an actual handheld gps. They were both w/in 1/2mph of one another. I figured that w/ the correct input on my edge of the actual gears and tire size i have that i was reading 6 mph over actual from 30 to 60 and then from 60 to 85 i was reading like 10 to 12 over what i was actually doing. So i adjusted the tire size from 35's to 32's and then it was right on the money. My edge mph is only 1mph under my actual mph from the gps. Is this weird to anyone else??????

 

The gps is going to be about as accurate as can be done. The edge however is working off mechanical inputs feed into the pcm. As you speed increases your tires are changing in size. This is from the spinning forces acting on the tire and heat increasing the pressure of the tire. I would think if you were within the 3% range or better I would be happy.