Tire size change alfaOBD

heckcat9

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UT
Ram Year
2016
Engine
Hemi 5.7
My recent experience with setting the tire size on my 2016 1500 with the latest AlphaOBD (v2.2.1.0) and MX+ reader...

I set my tire size to 2870mm per this post:

I had issues getting the settings to work without error codes so I finally tried a known working circumference from the AlphaOBD thread. That actually didn't work either...

My actual diameter per the manufacturer is 36.69 inches for my 37x12.5 Cooper SST Pros.
Actual circumference in mm:
2928 = 36.69 × 3.14159 × 25.4
The delta is 58mm between 2928 and the 2870 I used, which results in the speedo being mostly accurate and off by much less than a mile, GPS and radar verified. Good enough for me.

As others have mentioned, the truck indeed had to "rest" for the changes to propogate, strange. I shut the truck off, locked the doors, and grabbed a drink for 30 minutes and after my trailer brake, ABS, wheel speed, etc error codes were gone and my speedo and cruise control worked.

The AlphaOBD menus have changed a bit as well, below are the menu items I chose:
Car model: RAM 1500 (DS/DX/DT)
Function:
Body Computer > MY2013-2017 PowerNet
Engine > Chrysler PowerTech/Pentastar/World/Hemi v6/v8
ABS > Bosch/Continental/Teves/TRW PowerNet MY2013+ PowerNet

Hope this helps avoid the headache I had changing my tire settings the morning of an 8 hour road trip lol.
 
Last edited:

augiedoggy

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I joined to respond here. I also have used alpha to change the tire size on my 2015.. I have found it easier to just use "Torque pro" afterwards to clear all my codes if I get any at all. I found that when making small adjustments I dont always get any errors to clear. also there can be quite a time delay after changing setting. I have more than once had to walk away for a half hour. I also use a cheap $12 ELM327 obd bluetooth adapter I bought on ebay about 8 years ago. Ive since used it to also activate the rear view camera on my uconnect 5.0 stereo so I could add a cheap amazon backup camera. Ive also used it to turn on led and hid light options
 

Azbr06

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Arizona
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2017
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6.7
So I’ve been searching and can’t really find anything about my issue. New to the alpha obd program and has been working great so far. So my issue is, I have a 2013 2500 with 35s. I got the mm I used 2791 which was off but the question comes after I set that I go to abs and I know the changes the continental/ate so I chose the right one for my year, but when I click on abs initialization on the next screen the start and stop is greyed out. Any reason why? It has the steps but how do I know if my truck has g sensor or ESC? Thanks for any help
 

RAMRODDY

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SUDBURY ON CANADA
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2020
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HEMI 5.7
Just did my 2020 1500 Classic. A few things were different, Maybe I have a newer version of Alpha? Most notably, Ate/Continental was not an option under ABS. I used Bosch/Continental and it seems to have worked fine. No codes or lights after a brief test run. Speedo is within 1 or 2 mph of Waze or another route app at 60 mph. Close enough for me. Thanks!
Did you need to use a security cable to do this? Having a bit of trouble flashing after choosing tire size.
 

Bbroj

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2020
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Yes, I had a security cable. I may be mistaken, but I thought the security cable was only necessary for the newer 1500 Classics.
 
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