--Adjusting Computer for Tire Size

[bill4d]

Is there a paramter in the truck's computer that can be adjusted to compensate for different tire diameter's?

I'm already using a Superlift Truspeed, but I think I maxed out it's "infinite adjustability."

I'm thinking that if I adjust the truck's computer to it's maximum setting (assuming there is a way to do this), then the Truspeed will be able to accommadate a larger tire than it currently is.

[SmokeyWren]

The tire revs/mile parameter is stored in the ABS module. Cheap scanners won't access it, but with a Hickok NGS scanner you can access the ABS module and change the parameter.

Stock for your 2002 was 00655 revs/mile. The smallest parameter you can enter is 00601 = equivalent to some LT315/75R16 tires.

Here are old instructions for recalibrating the speedo. This will work on '99 - '04 PSDs. '05-up is different.
If you dealer's tech hasn't calibrated a speedometer on a SuperDuty before, he might spend an hour researching on how to do it before he actually does any work. After he has done a couple, then it's a 5-minute job – but most dealers will charge you one hour of labor to do the job.

If your service writer sounds like perhaps that dealership is not experienced in calibrating SuperDuty speedos, then copy and paste the following into a Wordpad or Word document, print it out, and give it to the service writer.

1) Ensure all harness connections are plugged in.

2) Using Rotunda New Generation Star (NGS) scanner and Version 3.2 or higher Service Card, Plug into the DCL connector.
• [ADDED: Do not use a service card version later than early 2001 model year. This will not work if you try to use a service card dated after the 2002 models came out. ]
• [ADDED #2: Ignore the above "ADDED" if you use the newer NGS Plus. With the NGS Plus you can calibrate the speedo on any 7.3L or 6.0L PSD.]
[*] [Added #3: Some techs now use the Ford Worldwide Diagnostic System (WDS) to calibrate the speedo. I don't know anything about how they do it.]

3) Turn Key on w/Engine Off.

4) Select Service Bay Functions

5) Select ABS Module or 4WABS Module depending on application.

6) Select Tire Size/Axle Ratio Configure.

7) Enter tire manufacturer's specification of revs/mile (tire revolutions per mile) into the NGS as the REV.PER MILE figure.
• [ADDED: To have an even more accurate odometer, enter the following rev/mile:

For 285/75R16 tires enter 00636
For 295/75R16 tires enter 00626
For 315/75R16 tires enter 00601

Do not try to enter a number less than 00601 with the old NGS. With the newer NGS Plus or WDS, I don't know. ]

8) Select Tone Ring size and verify that 120 is programmed in.

9) Select <Option> and press TRIGGER.

10) Select <Vehicle> and press TRIGGER.

11) Press <Done> and the Module will be reprogrammed.

12) Check Speedo accuracy.

To determine your odometer’s accuracy (if you don't have that fancy newfangled GPS stuff) just find an interstate highway that has two mile markers 10 miles apart without being near an entry, exit, bridge, or overpass. When your front bumper passes one of these markers, push the odometer reset button to zero. Ten miles later, your odo should read exactly 10.0, which is 100 percent accuracy. Every tenth of a mile off from 10.0 is one percent error.

Some Ford dealers will refuse to calibrate the speedo. They say it can't be done - or that they're not allowed to do it. So in that case just refer them to the 2003 Ford gobbledegook version of the procedures at:

http://www.fleet.ford.com/truckbbas/non-html/2003/bb_pdf/206.pdf

[reba]

Our Ford dealer charged me $85 to recalibrate my speedo.

It took the technician 90 minutes to get it right.

He stated it took him so long becasue he was having an arguement with the computer.

I checked the accuracy with a road side radar and it was spot on.

Call your dealer first because not all Dealers has this type of trained technician.

The important message here is; even if you know what you are doing it may take several trys.

[bill4d]

As usual Smokey, awesome information!Many thanks.I've actually had a similar reprogramming done at my dealer to compensate for my larger fuel tank. Now my overhead miles to empty reading acknowledges 46 gallons. I got lucky and they actually did it for free.

[TTBadDog]

My trucks speedo is dead on with two GPS units. The odometer however is off by 2 percent on the same two GPS units. Point being the speedo is correct but for calculating MPG I need to multiply miles driven by 1.02, this does not make a huge difference.

[bill4d]

That seems wierd. You'd think the speedometer would be directly tied to the odometer's reading. It may be false to say your speeometer is "dead" on. With an analog gauge you don't really have any degree of accuracy to estimate how fast you are going. For example you may think the needle is on 70, when in fact you're going 70.6 MPH. The odomter is a little easier to judge accuracy, because the value given goes down to the tenths place.

[SmokeyWren]

Originally Posted by bill4d

That seems wierd. You'd think the speedometer would be directly tied to the odometer's reading.

It is. They both use the same digital signal from the PCM. But as you noticed, the speedo signal gets turned into an analog output while the odometer/tripmeter is still digital. And the analog gauge doesn't read as accurately as a digital gauge. But I don't like digital speedos, so I'm glad ours is analog, even though it's not as precise as a digital.

[capterik]

Originally Posted by bill4d

As usual Smokey, awesome information!Many thanks.I've actually had a similar reprogramming done at my dealer to compensate for my larger fuel tank. Now my overhead miles to empty reading acknowledges 46 gallons. I got lucky and they actually did it for free.

I paid to have my speedo adjusted for my 19.5's and they didn't get it right 2-3 mph slower than checked with 2 different gps's. I asked them to change my fuel tank to reflect the 55 gallon one I repl,aced stock with and they told me they couldn't that it was built into the float inside the tank, argued that made no sense, but to no avail. Wish I had a tech like yours.

[KYmxracer52]

I've checked with my local dealer about doing my speedo for my 35's. They priced it at $85. I have a Edge Juice Platinum too. I thought they are suppose to recalibrate speedos. Does anyone know this for sure? I did the setup on mine, but it didn't mess with the dash speedo, just the digital one built in to the display.

[SmokeyWren]

Originally Posted by KYmxracer52

I've checked with my local dealer about doing my speedo for my 35's. They priced it at $85. ...I thought they are suppose to recalibrate speedos. Does anyone know this for sure?

Your question doesn't make sense to me. You say they will do it for $85. Most dealers will calibrate a SuperDuty speedo for about one hour labor rate, so it sounds like your dealer is "normal" in that respect. Yes, an experienced tech can do it in 10 minutes, but an inexperienced one may take two hours or more in research to figure out how to do it.

So what is your question?

For your 2005 and later models, the tech has to put in the size of the new tires, and the computer then comes up with a generic tire revs/mile for that tire size. No, it's not as accurate as the "old" way for '99-'04 models where they could change the actual revs/mile parameter in the computer.

[Delwars]

Originally Posted by TTBadDog

My trucks speedo is dead on with two GPS units. The odometer however is off by 2 percent on the same two GPS units. Point being the speedo is correct but for calculating MPG I need to multiply miles driven by 1.02, this does not make a huge difference.

I would be willing to bet you a few gallons of WVO that when you were doing you testing with the (2) GPS units that you went under a underpass, tunnel, tree or maybe a large billboard sign and your GPS lost signal for a split second. My Lowrance that I use in my truck and my dad's boat does this every time. There's nothing we can do about it, GPS is line of sight.

[SteveIn29]

Originally Posted by Delwars

I would be willing to bet you a few gallons of WVO that when you were doing you testing with the (2) GPS units that you went under a underpass, tunnel, tree or maybe a large billboard sign and your GPS lost signal for a split second. My Lowrance that I use in my truck and my dad's boat does this every time. There's nothing we can do about it, GPS is line of sight.

You have it wrong on this. While the GPS does need to have line of sight to the sky it isn't a line of sight device. A GPS operates by tracking the signals from multiple satellites (8 or more now days) and while the signal from any one (or more) of them might get temporarily blocked by buildings, bridges, mountains, etc the odds of ALL the signals being blocked is highly unlikely even in the city, though your tunnel suggestion would do it it it was long enough. The loss of one satellite's signal from going under a bridge, sign or tree (if it even happened) wouldn't affect the accuracy of the GPS unless you were only tracking 2 or 3 satellites.

[KYmxracer52]

Originally Posted by SmokeyWren

Your question doesn't make sense to me. You say they will do it for $85. Most dealers will calibrate a SuperDuty speedo for about one hour labor rate, so it sounds like your dealer is "normal" in that respect. Yes, an experienced tech can do it in 10 minutes, but an inexperienced one may take two hours or more in research to figure out how to do it.

So what is your question?

For your 2005 and later models, the tech has to put in the size of the new tires, and the computer then comes up with a generic tire revs/mile for that tire size. No, it's not as accurate as the "old" way for '99-'04 models where they could change the actual revs/mile parameter in the computer.

My question was, "Does anyone know if the Edge Juice Platinum will correct your speedo for tire changes?"

[bill4d]

Does anyone know what the new software some Ford techs are using now to do this type of reprogramming? When I went in to have the speedo recalibrated the tech did not use the old New Generation Star scanning tool. Instead he simply had a laptop and a cable connecting it to the truck's computer connection. I watched while he did it and the screen to enter the new tire size info simply had fields to fill in for height, aspect ratio, rim size and gear ratio. He entered in 395 85 R20 and 4.88 for my gears. After driving it though, there is no change in the speedo accuracy. It is still reading as if 31" tires were on.

[KYmxracer52]

Originally Posted by bill4d

Does anyone know what the new software some Ford techs are using now to do this type of reprogramming? When I went in to have the speedo recalibrated the tech did not use the old New Generation Star scanning tool. Instead he simply had a laptop and a cable connecting it to the truck's computer connection. I watched while he did it and the screen to enter the new tire size info simply had fields to fill in for height, aspect ratio, rim size and gear ratio. He entered in 395 85 R20 and 4.88 for my gears. After driving it though, there is no change in the speedo accuracy. It is still reading as if 31" tires were on.

I took my truck in to get calibrated, and the idiot there did the exact same thing they did to your truck. Mine is also still the same. Can't believe I wasted an afternoon taking it there and all the fuel I wasted as well, and it's still the way it was before. What's the correct way for them to do it?