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ENG430

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Is changing tire circumstances will change and recalibrate the transmission to the new tire size.
One of my friend said that I should reprogram the gear transmission if I change to bigger tire size or it will damge the gear box.
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UGADawg96

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I upgraded from 275/60r20 to 285/60r20 and the speedo is more accurate now. It was off from the factory.
 

ENG430

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Is changing tire circumstances will change and recalibrate the transmission to the new tire size.
One of my friend said that I should reprogram the gear transmission if I change to bigger tire size or it will damge the gear box.
Any help please?

Should I change the gear ratio when upgrading to big tires?
 

additionsola

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Any help please?

Should I change the gear ratio when upgrading to big tires?

It all depends on tire size and what your gear ratios are now... going up a few sizes isn't going to hurt anything. Hell going to 35s won't hurt anything, but you're going to kill your torque/low-end power. On my Chevy I went to 35s (from 31s) and definitely benefited from re-gearing. On the Ford, I opted for the 3.55 gears, I went to 33s and won't touch the gears.
 

ENG430

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It all depends on tire size and what your gear ratios are now... going up a few sizes isn't going to hurt anything. Hell going to 35s won't hurt anything, but you're going to kill your torque/low-end power. On my Chevy I went to 35s (from 31s) and definitely benefited from re-gearing. On the Ford, I opted for the 3.55 gears, I went to 33s and won't touch the gears.
The tires installed now in my F150 from Ford is: Pirelli 275/60/20 .

Im going to install: BF 285/55/20 .

is it safe to keep the same gear ratio that comes from the manufacture or should change it?
 

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additionsola

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The tires installed now in my F150 from Ford is: Pirelli 275/60/20 .

Im going to install: BF 285/55/20 .

is it safe to keep the same gear ratio that comes from the manufacture or should change it?

You're actually going down in tire size....

Ford F-150 How to use FORScan to recalibrate speedometer for bigger tires 1640383579283


You'd be A-OK keeping stock gears.
 

Eric12775

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What about when changing axle gearing? I’m planning on installing a 3.73 posi in my rear and I’m probably going to go up from 17s to 22s.
 

itsdchz

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You'll be able to calibrate your speedometer with the free FORscan software, a portable Windows device, and an appropriate ODB II adapter. The best adapter to get is the ODBLink EX for about $50 on Amazon. Stay away from the chinesium ones.

I have instructions for doing this here: https://www.mustang6g.com/forums/th...ometer-error-no-flash-or-tune-required.67564/

Pay close attention to the need to do a PCM and TCM relearn in order to clear DTC's.

Also, for the 2021+ F150 the address location has changed. Instead of:

726-12-01 xxxx ABCD xxxx

It is now split between two lines:

726-15-01 xxxx xxxx ABxx
726-15-02 CDxx xxx xxxx

The same values from my calculator linked in the Mustang 6G thread will work in the new location.
Help??

I have gone from 265/60/20 stock Hankook to 275/60/20 more aggressive Cooper Discoverer ATS. When pulling up my info in a 2021 Powerboost, under BdyCM, I look at the appropriate fields but they do not match:

Stated info from OP: 726-15-01 xxxx xxxx ABxx - This field already contains the correct value in my vehicle: xxxx xxxx 09xx (based on code gen, both sizes have this same value present)

Stated info from OP: 726-15-02 CDxx xxx xxxx - This field only has the parameters in 2 segments, ie: F3xx xxxx

Based on my stock configuration, I should have 726-15-01 as: xxxx xxxx 09xx - this is the same for new parameters as that value did not change - OK

What would I change for 726-15-02? My stock parameters are: F3XX xxxx (no 3rd segment) (the stock parameters in the HEX generator suggests that based on 265/60/20, I should be CD- CDxx xxxx xxxx, even though F3 is present on as built parameter)

The Hex generator states I should have F2 as the new value, however when I replace the F3 to the new F2 value, it states that my checksum is wrong, so I did not write The code and perform the DTC check.

Any ideas if the Powerboost BdyCM and 726-15-02 is different on 2021+ and should only contain 2 segments, not 3, and if I write the F2 value vs F3, if this is truly for the tire size?

Thanks in advance.

In summary:
As built on 2021 PowerBoost - came with 265/60/20 Hankooks- Added 275/60/20 Cooper

I have stock configuration:
726-15-01: xxxx xxxx 09xx
726-15-02: F3xx xxxx

Hex builder states I should have stock configuration as:
726-15-01: xxxx xxxx 09xx
726-15-02: CDxx xxxx xxxx

Hex builder with new tires:
726-15-01: xxxx xxxx 09xx
726-15-02: F2xx xxxx

Forscan v2.3.46
 
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Choad92

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Does anybody know if changing tire size using Forscan will create issues with an aftermarket tuner? The reason I ask is because I just put 35s on my 21 RCSB, and I have a tuner on order form Livernois. I assume the tuner will allow for tire size changes as well. If I go ahead and change it now with Forscan will I have issues? Just wondering if there would be conflicting values in these modules since it is being changed using two different tools ect. This might be a question for the Livernois guys but I thought I would check here first. Thanks all.
 
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z-man

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Has anyone else notice their values for 726-15-01 and 726-15-02 change after programming?
 

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NVSTG8R

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Yes, just used FORScan to update my tire size from stock 22" to 35 x 12.5. It worked. The only issue I had was that the spreadsheet does not allow you to put in 35" tires. You have to find the equivalent using the standard format. So I used 315 65 20's. Initially my truck would show I'm driving 75, when GPS said I was doing 78-79. After the fix, I was actually slower. When my truck showed 75, GPS said 74. So I used the second step on the spread sheet and entered the speed difference. It gave me the knew digits to add and now I'm right on. If you use the main FORScan thread, and pull up the spreadsheets, you'll know what I'm talking about. Works great and very impressed on the work they did to make the spreadsheets. Thank you to all. With that said, if you need help, reach out. I just downloaded FORScan and used it for the first time to do this, not hard.
 

cheesedogf150

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Coming from German vehicles, the speedo has always indicated a higher speed than gps/radar/laser

not a bad thing
 

minirx7

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Yes, just used FORScan to update my tire size from stock 22" to 35 x 12.5. It worked. The only issue I had was that the spreadsheet does not allow you to put in 35" tires. You have to find the equivalent using the standard format. So I used 315 65 20's. Initially my truck would show I'm driving 75, when GPS said I was doing 78-79. After the fix, I was actually slower. When my truck showed 75, GPS said 74. So I used the second step on the spread sheet and entered the speed difference. It gave me the knew digits to add and now I'm right on. If you use the main FORScan thread, and pull up the spreadsheets, you'll know what I'm talking about. Works great and very impressed on the work they did to make the spreadsheets. Thank you to all. With that said, if you need help, reach out. I just downloaded FORScan and used it for the first time to do this, not hard.
Did you have to relearn TCM/BCM?
 

NVSTG8R

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On the spreadsheet, it brings up resetting two different modules. My truck only had the one (TCM) I believe. When you look at it, it's got a tab that says relearn. Just click it and your done. Because it said to do it, I hit the relearn. So to answer your question did I have to? I don't know, as I just did it. No issues though, after doing the relearn. I assumed this was necessary for the adjustments made, so I just did it.
 

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Can someone who had 275/60R20 tires from factory on their 2021+ tell me what your default values were? I just got a great deal on some 20” Chrome takeoffs so I’m going to upgrade from my 18s. Figure the default values from as built trucks with the tires should work flawlessly.
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