Setting arbitrary tire sizes for speedometer calibration

[ggandzz]

hi， I have a few questions to ask you. If you only change the tire size, can the relevant ABS or other safety aids work properly? For example, Mustang 2015-2.3T-255-40-19, according to your formula, the original value is 208 5, that is 0825. If I change to 275-35-20, will it become 2128, that is 0850? Is the power conversion factor calculated according to 96.7% or else? Please give me a hand.

[Aussiejoe]

Does anyone know if it's possible to change tyre size on a 2008 transit van fwd 2.2? Thanks

[dcag14@verizon.net]

I have a 2015 Ford Fusion Titanium. Ever since I bought it there has been a 2 mph speedometer error compared to GPS - at 70 mph on GPS, speedometer reads 68. Used the spreadsheet calculator found elsewhere on this forum to change BCM 726-12-01 from xxx-0804-xx to xxx-07CB-xx. Test drove right away. Amazing! Speedometer exactly matches GPS now.

Tire size is 235-45-18. Stock for Titanium trim.

[jeff6146]

DCAG14, that's pretty normal to only be off 2MPH. That's why we wont issue tickets for that unless you run across an a**hole having a bad day. But it is his/her discretion as to when or when not to issue a ticket. most of the time they pull you over to just inform you so you are aware. but to answer your question, someone posted a formula to get it down to the money. someone else had a good idea and that's to check it after using GPS, or just let a cop tag you with a radar.

[jeff6146]

Here is my problem, when I try to reset the tire size and perform the function none of the tire size configuration’s in the module will work. So I can’t get past even riding the module for the tires as I have. Has anyone else put 35x12.50x17’s on their 2015 F350 Dually? Mine is a Lariat FX4 which I’ve upgraded to the sync3.

This is what should have worded
Toyo Open Country MT 35x12.5x18 726-12-01 xxxx 0A50 xxxx

So I then tried everyone of these and none would work.

BFG KO2 35x12.5x20 726-12-01 xxxx 0A7F xxxx Freeseframe
Nitto Ridge Grapplers 35x12.5x20 726-12-01 xxxx 0A57 xxxx dominatorlp
Toyo Open Country A/T 35x12.5x20 726-12-01 xxxx 0A8F xxxx Kaye Kolb Jr.
Toyo Open Country MT 35x12.5x18 726-12-01 xxxx 0A50 xxxx Timc74
Nitto Ridge Grapplers 35x11.5x20 726-12-01 xxxx 0A3D xxxx gonethinkn
BFG KO2 34x10.5x17 726-12-01 xxxx 09FF xxxx 17x7 (Dually) ZooDad
BFG KO2 315/70/R17 726-12-01 xxxx 0A68 xxxx robbieg
BFG KO2 305/65/18 726-12-01 xxxx 0A21 xxxx DeltaNu1142
BFG KO2 285/70/17 726-12-01 xxxx 09E7 xxxx jpeckinp
Cooper AT3 275/70R18 726-12-01 xxxx 09E7 xxxx Scott91370
Falken Wildpeak A/T3W 275/70R18 726-12-01 xxxx 09E7 xxxx waphilips
Michelin LTX A/T2 275/65/20 726-12-01 xxxx 0A45 xxxx TX-FJuan50

[Andyfocus]

have you tried resetting to as built and do it then change the sync because you have changed the unit ?.
at least then you can use the original tyre size setting and leave it alone till a solution is found ?

[jeff6146]

the tire size is at the as built. its the same numbers.

[jeff6146]

Perhaps run the force adapt learn the codes in it so it thinks nothing has changed? I seen someone talking about how to make the ecm learn the new stuff and forget the old stuff. not sure where I seen it, id have to find that. maybe someone on here can lend a hand if they have it saved.

[BOSSC351]

275 65 20 Radar Renegade LT tire on a 2013 F-150. Spreadsheet shows 0A45. I input this and I am 6 MPH off. Speedo shows 70 and I am traveling at 76 per the GPS. I have tried the GPS calculation and still off by about the same. What in the world am I doing wrong?

[Dordogne]

275 65 20 Radar Renegade LT tire on a 2013 F-150. Spreadsheet shows 0A45. I input this and I am 6 MPH off. Speedo shows 70 and I am traveling at 76 per the GPS. I have tried the GPS calculation and still off by about the same. What in the world am I doing wrong?

As far as I know, this doesn't work on the 2014 and under F150's. I believe it is indeed stored in the BCM, but a different location. I would set your as-built back to stock in case you inadvertently changed something unrelated to the tire size.

If anyone has been able to get this to work with a 2014 and under, post up what you did so others can try and replicate it.