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Change tire diameter / revolutions per in ECU

Built4Speed

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How can I cheaply change the tire diameter / revolutions per mile parameters in the ECU/tune for tires that are different in size that stock?

I have a rear set of drag radials and I would like to easily change the Parameters as I will be swapping them at least monthly.
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armykyle1 [HACKED ACCOUNT

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How can I cheaply change the tire diameter / revolutions per mile parameters in the ECU/tune for tires that are different in size that stock?

I have a rear set of drag radials and I would like to easily change the Parameters as I will be swapping them at least monthly.
Do you have an SCT?
 
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Built4Speed

Built4Speed

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Do you have an SCT?
No.

I wonder if there is one of the Bluetooth OBDII port devices that would connect to an Android phone would work?
 

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Built4Speed

Built4Speed

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I thought it was not possible on SCT with S550?
I called Roush (I have the Roush TVS) yesterday and spoke with their technical department and they recommended I get a tuner from American Muscle or CJs, but it looks like they are all @ $400.

I don't really want to spend that much just to be able to change the tire diameter parameters at will. I don't need the "tune" part of the tuner since I am sticking with the stock Roush 670hp tune to keep the bumper to bumper warranty intact.
 

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Check the As-built thread in the DIY section. You will need a laptop and a blue tooth OBDII reader. I corrected mine this way in the as built data. There is a calculator buried in the thread somewhere. It was also posted in the tire and wheel section as well. There is also the whipple flare device but still requires a laptop.

Tire size and gear ratios are store in the BCM not the ECM.
 

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Only device that can do it is the Whipple flare tool. There's a few threads that detailed it. I couldn't even get the dealership to fix my speedometer and it's off by 5 mph off on the cluster and cruise is off by 2mph.
 
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Built4Speed

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Ahhh, now we are getting somewhere. The Whipple flare tool is $275, that's certainly better than $400.

Thank you for the contributions.

BTW, what does "BCM" stand for?
 

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It's stored in the BCM, can't be changed with HPT or SCT from what I recall. You would have to use the whipple cable or check with your dealer to see if they can update it using the Ford tool
 

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BCM is the body control module.
 

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Whipple Flare tool is the only way to change gearing, tire size, etc in the S550. Because its stored in the body control module. The flare tool is made to order specific to the vin number you provide. Its a one time marry device as well.

If you car is a stick its not really that important to change the tire size in bcm. Your speedo will be off but not by much.

If you have an auto it will impact shift points for the transmission and speedo as well.

Goodluck!
 

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Check the As-built thread in the DIY section. You will need a laptop and a blue tooth OBDII reader. I corrected mine this way in the as built data. There is a calculator buried in the thread somewhere. It was also posted in the tire and wheel section as well. There is also the whipple flare device but still requires a laptop.

Tire size and gear ratios are store in the BCM not the ECM.
^^^ This. Why spend 275 on a Whipple Flare Tool when a 50 dollar OBD adapter and free software can do the same thing (plus enable some other cool stuff)?
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