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looking to adjust my tire calibration on my sct but dont know which one it is since its not actuall tire size. i have 35x12.50x17 can anyone help out thanks
 

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Place a mark on the ground and on any tire at the 6 o'clock position. Roll the truck making one complete revolution and stopping the tire mark at the 6 o'clock position again and mark the ground. Using a tape measure find the distance between the marks in inches. Using 63360 (inches in a mile) divided by the measured distance in inches will equal your tire revs per mile. Just round up or down whatever is closest to the value you can enter into the SCT ( IE your revs equal 609 use 610, etc...) 66360"/104"= 609

Dont forget your tires will get smaller so the revs will go up over time so maybe rounding up will be a better option.
 

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you could also look at the specs sheet on the tire manufacturer's web site...
 

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I have dick cepek 35's and i'm using 590 revs per mile. It is still about 4mph fast, so when I feel like retuning I will use 585 or 580. I would rather my speedo be faster than the truck rather than vice versa...
 

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I have dick cepek 35's and i'm using 590 revs per mile. It is still about 4mph fast, so when I feel like retuning I will use 585 or 580. I would rather my speedo be faster than the truck rather than vice versa...
From what I have gathered the 6.0 CANNOT have the speedo recal through the SCT. The SCT has that setting for shift points and cars that it will change. I have tried many things with my 35's and it was always 4mph fast @50mph. The only way to do it is through a tru speed or something hard wired.
 

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Hmm, thats not what ive always heard and It went from being 8-10mph fast to only 4 with my last change of the rev's per mile...or maybe i'm crazy?
 

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Hmm, thats not what ive always heard and It went from being 8-10mph fast to only 4 with my last change of the rev's per mile...or maybe i'm crazy?
There is always a chance I could be wrong but I had a fairly big thread on this and it came to the conclusion that the SCT could not do it. I was also told Ford could do it, I went there and they couldn't either. AE can do a 7.3 but not a 6.0. I may just plug my SCT in tonight and put a ridiculous rev/mile number in and see what happens.
 

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There is always a chance I could be wrong but I had a fairly big thread on this and it came to the conclusion that the SCT could not do it. I was also told Ford could do it, I went there and they couldn't either. AE can do a 7.3 but not a 6.0. I may just plug my SCT in tonight and put a ridiculous rev/mile number in and see what happens.
I was considering doing the same thing actually lol...lemme know what you find out if you do!

btw, i'm using gps to figure out my mph
 

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Hmm, thats not what ive always heard and It went from being 8-10mph fast to only 4 with my last change of the rev's per mile...or maybe i'm crazy?
Must be crazy. SCT does not alter the speedo reading on our trucks, only corrects the tire rpm for shifting purposes. Ford can recalibrate your speedometer, but it is not very common, and the average tech prolly does not know how or have the time to mess around doing it.
 

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Must be crazy. SCT does not alter the speedo reading on our trucks, only corrects the tire rpm for shifting purposes. Ford can recalibrate your speedometer, but it is not very common, and the average tech prolly does not know how or have the time to mess around doing it.
That is what I thought....
 

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:whs:
 

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I used my gps as well.... it was wvery close to matching the speedo with my tow file loaded.....
 

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Measuring the distance as I described will give you exactly what your truck/tire/wheel combo are actually turning. I used 595 for my 35's and recalculated it as above to 610. Tranny shifting is different than before so it made a change. The tire specs through the manfacturer might work but that's not necessarly on the same size wheel you are running.
The method above takes maybe 10 minutes max.

If you want Ford to recal the speedo tell the Service Department to recal the ABS module. This is what feeds the speedo the data for the speed.
 

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Measuring the distance as I described will give you exactly what your truck/tire/wheel combo are actually turning. I used 595 for my 35's and recalculated it as above to 610. Tranny shifting is different than before so it made a change. The tire specs through the manfacturer might work but that's not necessarly on the same size wheel you are running.
The method above takes maybe 10 minutes max.

If you want Ford to recal the speedo tell the Service Department to recal the ABS module. This is what feeds the speedo the data for the speed.
Ford would not do it for me. Maybe some dealers are different but the ones around here wouldn't touch it. I just bought a tru-speed that I am going to throw in this weekend, then I will be good.
 

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The new Autoengunity can do it by tapping into the ABS module where the speedo calibration is held.
How new? I spoke with them a while ago (maybe a couple months) and they said it will do a 7.3, but not a 6.0.
 

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King Dingaling
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I have a Speed Wizard,...cheaper than a True Speed,...and it can be calibrated while parked, no screws like a TS, and it is way more user friendly.
 

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I have a Speed Wizard,...cheaper than a True Speed,...and it can be calibrated while parked, no screws like a TS, and it is way more user friendly.
Wish I knew about that one, o well. I got my tru-speed used so it wasn't too bad, but counting turns can be a pita sometimes...
 

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Hmm, thats not what ive always heard and It went from being 8-10mph fast to only 4 with my last change of the rev's per mile...or maybe i'm crazy?
What year truck do you have? I wonder if the 03-04 trucks with the older cluster will allow the SCT to recalibrate while the 05-07 trucks with the newer cluster won't.

Just kinda thinking out loud on this and going off what I have heard/read about other things that require the actual cluster to be reprogrammed, such as adding a factory towcommand brake controller to an 05 truck that wasn't originally equiped with it.
 
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