Alfaobd issues with programing tire size

[Marcus67]

Hello Guys and Gals. First off I want to say I messed up in the beginning by not recording and saving my factory settings. I saw that video after all of this happened. So on my 2018 Ram 2500 bighorn, I started using Alfaobd to correct my tire size. I was trying to program my tire size to correct my speedometer because I changed wheels and tires. The factory size was 285/60/20 and the tires I got were 285/55/20. My speedometer was about 3 miles fast at 60 mph. I looked under the preset tire sizes and there were none the same size as mine. I found online a tire size calculator that switches it to mm. The calculator said mine was 2581 mm. So I manually entered that into the box, set it, and went and cleared codes and reset everything. All lights were off. Went and drove it and it was WAY off. At 55 mph according to my GPS the speedometer was reading 99mph. So I started dropping the number until I got down to 1787 and it is still off by about 10mph. Alfaobd or the computer one will not go any lower. I can enter any number I want but the "Static ECU Initialization" under ABS will fail and all my lights are going off.

Maybe I am off and need to go back up with my number, I just do not know. If I had the original number in mm I would just go back to it but my dumba__ did not record it.

Any help would be greatly appreciated.

 

[Marcus67]

I figured it out. I was paying attention to the digital readout, not my actual speedo. I guess during the process of reprogramming the tire size it reset the digital speedo to kmh instead of mph. Just in case this helps someone the actual number I used was 2550 and I am 1 mph off at 60.