I just got my truck re-geared from 3:73's to 4:56's. (I have 35's).

I put in the correct tire circumference, and correct gear ratio into my edge programmer, but my speedo still reads fast. Any help?

I am going down the freeway, and it shows I am going 85-90, and I know I am not going that fast. I cant figure out how to get the speedo corrected using edge.

 

you need to ajust the points up a little , on the X-2 its rotation per mile with my 35s that 595 , before I hade a different tunner and you measured from the ground to the top of the tire with a level say 34.75 inches and entered that .
To truely set it correctly you need a GPS unit or in my case a friend driving next to me.
Whatever the case you need to ajust tire size or set your gears

 

Your PCM may "think" your tires are bigger than they really are. Did you account for "squish"? Bill recommends reducing the actual tire circumference by 3%, and in my case at least, this was just about right.

- Jack

 

Yeah, I entered in 34.5" (for the edge, it is circumference...2751mm), which it what the measurement is from the ground to the top of the tire.

Even if I am off by about .5", it would be close. It is noticeably off.
I just don't want my truck to show more miles than it actually has because of this.

 

I think you'd be closer with around 2713mm. Using the "measurement method" you really want to measure from the ground to the center of the wheel. All the squish is at the bottom, so that distance represents the "rolling" radius. Then, multiply by 2 and then pi.

This reduces your distance traveled per rotation a bit and should reduce your "indicated" speed too. Although I don't know if it will be correct yet.

Bill says Ford sets the speedo about 2MPH fast anyway. We can only guess at their reason for doing so.

- Jack

 

In rethinking this a bit more, my advice on tire size would only change your speed by about 1 MPH (at 75, if my math is right).

Is it possible the Edge is not "holding" the gear ratiio and tire size you are setting?

When you go into the "Set Custom Program" menu and choose "Load Previous Settings" (or something like that), do you find that your gear ratio and tire size is what you set it at?

I seem to remember in another thread somewhere someone saying if you did not "set" the gear ratio at the same time as setting a new tire size, one or the other of them would revert to "default". I never found this in the manual though.

I DO know unless I "Load Previous Settings", that my tire size will be way wrong if I check it (when I try to adjust something else like WOT shift points).

These are just thoughts. The only expert around here is Bill. Why don't you PM or call him?

- Jack

 

Thanks for the help..... I am not sure who Bill is though.
Is Bill from edge?

When I program for level 2, I just change the tires and gears and then "done" and it reprograms. In other words, everytime I have adjusted the tire to see if it would make a difference, I would make sure I changed the gear ratio also.

What is the current update from Edge? I haven't updated the programmer in about 6 months.
I skeptical because of the issue they had with them working on 2007's. If it ain't broke, don't fix it.
I did notice, that I am not able to create a custom tune using the level 3 program.

 

Sorry bout that. Bill USED to be with Edge, but now is in business for himself. He goes by the login name ASEMechanic when he posts here.

Edge has decided to divorce themselves from "custom" tuning so they can be fully compliant with emissions laws. Bill is buying Edges now, "rebranding" them as "Gryphon" and selling them as programmers that CAN be custom tuned (by him).

His website is http://dygytalworld.ehost-services105.com/php/ and it's known as "PowerHungryPerformance". In spite of the fact he no longer works for Edge, he has stated he will do everythng he can to help Edge owners who are having problems - for free! Just call or email him.

The current update is dated about December 2007 I believe. I put it on my unit and everythng worked fine.

- Jack

 

I don't know if this will help you out or not but on my truck I had to set the tire circumference to just over 2600 for my 35x1250x17 BFG's. It is now about dead on with my gps unit. The edge owners manual said for 35's to run 2792 if I remember correctly - but that was way off. Not even close to being accurate. I just reprogrammed it a few times until I had it dialed in. I think I ended up going with 2610.

Edit: I still have the OEM 3.73 gears too though - all I did was make sure the edge was set to 3.73.

 

I will give that a shot. It seemed Ok when I had 3:73's, but I will try taking the tire size down a little. I don't have a GPS, so it is hard for me to check it without having me drive next to a friend and yell out the window.

 

just thought i would point out that the gear ratio has nothing to do with the speedo on these trucks.

 

I thought gears had everything to do with the spedo,(04-08years) look on top of the diff at the wires going in thats for the spedo it measures rotation , the menechic showed me when they did mine

 

the sensor on the rear diff reads off of a tone wheel that is part of the differential case which your ring gear bolts to. the differential case always turns at the same speed regardless of gears. the only time the speed of the case is changed is when larger or smaller tires are installed. a smaller tire makes the case turn faster, a larger tire makes the case turn slower. the speedo is only affected on vehicles where the speedo runs off of a cable rotated by the output shaft of the transmission/t-case.

 

Gears do affect the speedo, because mine used to be correct and is now way off when I switched to 4:56's. That is the only thing I changed. (From 3:73's to 4:56's.)

No matter how you look at it, gears or tires will make a difference.....

 

no. it wont. i know how the system works. you dont.