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Discussion Starter #1
I changed tire size (moved down a little closer to stock) and need to get my speedo reprogrammed at the dealership.

I am running Matt's SRL+

Do I need to return the truck to stok before going to dealer?
Will I need to get an updated tune after going to dealer?
 

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What are the current PCM/FICM strategies?? I don't recommend letting the dealership do any form of programming. You can use an up to date SCT SF3 to adjust the speedo.

If you go to the dealer return the truck to stock.
 

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Prolly be best just to get with Matt and get him to write you another tune that will correct your speedo. A tune shouldnt cost more than the dealer doing it.

I may be wrong but I think that is why the tuner needs the tire size for the custom ones!

If you take your truck to the dealer with a tune loaded it will mre than likely be wiped out and you will also lock your SCT up because it will still be married to the way the truck was!
 

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:dunno::dunno:Before I can even load a tune it asks if I want to change the tire revs. I can adjust mine around pretty easily. What you really need is the actual measurements for the tire revs. Measure the distance in inches it takes to roll the tire one full revolution. Then divide the inches in a mile by that number. This is a good starting point to correct the speedo. I got mine to within 1 MPH based off of GPS running 35" Toyo ATs.
 

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:dunno::dunno:Before I can even load a tune it asks if I want to change the tire revs.
Ya my X3 asked the same thing before I loaded the tune. I didnt mess with it tho, im only 2 mph off
 

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I had ford do mine before I loaded any tunes. Then again Vivian said that the strategies I had were absolutely ancient and she could do a lot more for me if I went and got the most up to date ones. So I had them adjust it while they were there and they can only adjust up to a 35" tire so it helped but I have basically 37s so mine is still off. My SCT gives the option to change revs too but I have not played with it.

Definitely go back to stock before you go back to the dealer, no matter what you are doing there. I hear they like to update strategies without asking people.
 

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SCT does not recalibrate your speedometer. It does ask for tire revs, but that is only for shift point corrections. The speedometer is calibrated in the ABS module, which SCT does not communicate with, only the higher end diagnostic tools like Ford's, Snap-On, and AutoEnginuity have that capability.

OP, you say you are going closer to stock. Are you sure the speedo was calibrated for the larger tires already? Maybe going back to stock size tires will make it more accurate. Check with a GPS to be sure. Dealership will charger you $80+ to recalibrate and they probably won't get it right, so put that chunk of change towards an AutoEnginuity and you can do endless free speedo tweaks to get it right and will also have a great diagnostics tool.
 

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I have changed my PCM and ABS modules to read a tire size with revs/mile close to my 33" A/Ts. There aren't a lot of choices in IDS to use as far as tire size goes and a lot of them are stock sizes. If you are running a much larger tire than stock it won't even let you go past a certain size.

Older IDS calibrations would let you manually enter revs/mile. Not anymore, ford did away with that.
 

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AE lets you enter anything from like 31 to 42, something in that range, and you enter it in inches down to 1/4" intervals. I'm guessing AE translates it to a revs/mile entry. Funny note, with my 35" tires, I had to enter something like 33.25" for it to be accurate.
 

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AE lets you enter anything from like 31 to 42, something in that range, and you enter it in inches down to 1/4" intervals. I'm guessing AE translates it to a revs/mile entry. Funny note, with my 35" tires, I had to enter something like 33.25" for it to be accurate.
Same here. My 35" trail grapplers measure out at 35" exact but I still had to enter in 33.25 in AE to correct the speedo. That's shorter than the stock 275s that came on the truck.
 

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Mine doesn't ask me to change the tire revs it gives me the choice to adjust options but it hasn't ever changed the speedo when I set the revs per mile.
Now that I think about it, Vivian told me the revs per mile on the sct was for shifting only because the speedo uses the ABS sensor, not the trans.





AE lets you enter anything from like 31 to 42, something in that range, and you enter it in inches down to 1/4" intervals. I'm guessing AE translates it to a revs/mile entry. Funny note, with my 35" tires, I had to enter something like 33.25" for it to be accurate.
Anyone nearby have AE or want to send me all your stuffs to borrow? I would pay to have it adjusted just so I could get an accurate MPG reading.

My RAZR made me send this...
 

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Discussion Starter #16
I moved from a 35" tire (I had the speedo corrected for 35's before custom tune )

Now I have 33" tires and custom tune. Need to adjust speedo and then reload custom tune.
 

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Funny I forget about this. Back in the day I installed Pioneer AVIC head unit with Nav. I have gotten so used to looking at my GPS speed, I never look at dash speedo ever. I had dealer reprogram tires once, max is 35s, SCT cannot. Tire revs for tranny, not speedo. I firmy believe custom tunes can NOT change speedo, as it is taken from the abs module and the pumpkin ring. But it sounds like some of you say it's been done. I do have the older SCT, but I don't see how the newer ones could interface with ABS module. Anyway, if you guys get Nav systems installed you can just view gps speed, much easier and never have to get dealer to reprogram at all. Just a thought.
 

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I moved from a 35" tire (I had the speedo corrected for 35's before custom tune )

Now I have 33" tires and custom tune. Need to adjust speedo and then reload custom tune.
Since tire size is programmed in the ABS module, you can do it before or after retuning, it doesn't matter.
 
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