Regarding tire size and adding that change via the IID tool to adjust the speedometer readings I'm having a little trouble figuring out what to do, and this is after reading the manual too. In the CCF file I am able to update specs (see my attachment) from 255/55r19 to 265/65r18. Most of it is pretty obvious/clear, such as changing the aspect ratio, width, rim diameter and rolling radius but where I'm confused is the rolling circumference. I "think" I should be changing that value to 2517mm but it seems I'm unable to do so, and for Tire size MSB I have no idea what to put there. I have not yet reached out to GAP but the only documentation I found in their FAQ was this -
https://www.gap-diagnostic.com/faq-items/adjust-speedometer-fitting-bigger-tire-tyre/
Any thoughts? Or should I just not bother and not worry about the speedometer difference. I don't want to mess with too many settings if it's not actually beneficial.