You don't have to remember the old value. Just figure out the correct number of the current circumference . Very easy to do.I changed my tires and wheels on my 2020 Lonestar. When I tried updating the size on alfaobd it caused my speedometer to be over by 2 mph. I've tried to go back in numerous times to change the size around to correct the speedometer with no avail. Also my front and rear park sensors went unavailable. Can any one help get things corrected?
OEM tires were 275/65/18
Changed to LT285/55/20
Right at the center of your wheel, measure from the bottom of your wheel to the top of your wheel in mm. Very important that you use mm to measure. Then, take the value times with 3.14 (pi) give you the new circumference value. Note: pi is 3.14.
Example: I measured my wheel as shown in the photo, I got 820mm. Take 820mm x 3.14 = 2574.8 mm >>> round up to 2575mm. I enter 2575 to Alfa.
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