Tire size/alfaobd help needed

[HCM1970]

Can anyone with an alfaobd and the stock 20" tires let me know what size in mm is stored in the BCM?
Im having a hell of a time getting the speedo to read correctly against my gps, with every change it either reads faster or slower. Somebody help lol

 

[sjhdu]

I went from stock 17" to stock 20" and the above preset set me to 2570 mm and it was perfect.
My Ram is a 2022 Classic. When I was researching all the configs I could find for stock 20" show 2640 mm, I don't know why. I guess yours could be one or the other.

 

[HCM1970]

Thank you so much!! I have it set at 2631 right now, also tried 2648,2650
I dont get it though 275/60/20 is 103.6" which is 2631.44mm

 

[62Blazer]

Out of curiosity, how far off was the speedo from the GPS? The difference between 2631 and 2648 is just over 1/2%, which at 65 mph should be less than 1/2 MPH (at least on paper).