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Discussion Starter · #1 ·
I'm running Goodyear 275/60r20 and my speedometer is 2 miles an hour off (gauge shows 40 I'm actually at 42). I checked speedo calibration via alfa and it shows that I'm set for these tires...but the mm is approx 2500 something saved for these tires, the real circumference is 2717.8, and there is ability to change for mm incase your tires not listed. However when ever I do the enter manual option , alfa
Does anyone know a work around ? I've read the guide to change the tire size several times and am doing what it calla for.
Normally wouldn't worry but am teaching my daughter to drive and she drives quite a it of different vehicles between my xs house and mine and would like her not to have to compensate on my truck
 

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Here is a good instruction.
Notice the second step on page 3, ABS MODULE RESET. Sometimes this is required, sometimes not.
Be sure you are using "my2016-2017 power net". Do not use the "2013-2017".
 

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Yes, you can set tire height in mm with AlfaOBD.

You can also play around with other tire sizes and see what gets the speedo accurate. Set a tire size, test, repeat.
 

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Yes, you can set tire height in mm with AlfaOBD.

You can also play around with other tire sizes and see what gets the speedo accurate. Set a tire size, test, repeat.
That's what I had to do. I gradually changed the mm until my Speedo and Odometer matched my two GPSs. It took a few test runs but was worth it because I'm anal for accuracy.
 
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Discussion Starter · #5 ·
The issue is when I use the manual number it fails. So the good year tire size I have is evidently not the true circumference manufacturer info shows 107" circumference which into mm is 2717.8 not the 2570.....I can get it to work for any of the preloaded functions/tire specs only fails when I don't select one and enter the circumference manually...
 

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Discussion Starter · #6 ·
Does anyone know why the option to add your own size in mm seems to not work correctly ? I've went thru the list of pre selected sizes and do not see any that should need to be checked. Nor do I know any of them that would be closer to reality of 2717.8 circumference
 

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Discussion Starter · #7 ·
No ideas darn...don't know why the manual selection doesn't take...it will take any of tire selections...anyone know out of the list what would be closest to 107" circumference ( or 2718 mm)...

I run Goodyear 275/65r20s I believe, the pre saved circumference is 2505 and needs to be 2717.8
 

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2505 seems to align roughly with a default/stock tradesman trimmed size 265/70/17
 
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Discussion Starter · #9 ·
Hmmm ok, I've never went past step 1 since I can't get it to accept 2717.8, so maybe it's set at the "right" tire in step one...I'm away for 4 days when I get home ill check step 2 &3
 
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