Tire size change alfaOBD

[Justin33]

I just did 2 tire size changes yesterday morning, one on a 2017 and the other on my 2019 classic. I wrote down and printed instructions just to be sure I followed them to a t. My truck was off about 2.8%, 2 mph at 70. I added 2.8% to the oem setting and programmed it. Had zero faults pop up. When I went to do the initialization, it wouldn't give me that option, on either truck. Cleared rolls information. Cleared the faults on all modules, even tho it didn't have any. Settings took on both trucks, speedometers are both accurate. My tire size was 275/65/20, the other guy was 35/12.50 (set circumference at 2714).
Is it possible that if you change the settings, you may not need to do all the abs stuff? Fwiw, the truck seems to perform better, feels stronger off the line and the shudder I had on take off seems to be gone.

What size are you using in mm as I can’t get the truck better than 2mph off. I have 275 65 duratracs but can’t find the sweet spot. Right now when truck is going 70 I’m getting 68 on phone gps.

 

[hunterdan]

What size are you using in mm as I can’t get the truck better than 2mph off. I have 275 65 duratracs but can’t find the sweet spot. Right now when truck is going 70 I’m getting 68 on phone gps.

I'm not sure. I'll have to check and let you know.

 

[Justin33]

I'm not sure. I'll have to check and let you know.

Yes let me know as when I’m going 70 Via gps on phone the truck is showing showing 68

 

[paul10053]

Quick write to help with this. However I bear no responsibility for any changes that you might not like. Only ones you do.

Start off with key in run.
Open app
Select dodge/ram button, Ram 1500 or 2500 From drop down, Body Computer, then body computer MY2013-2017
Connect then click on the icon at the bottom with the hood open
From the drop menu select "Program tire size"

Right above start on this page is a text box that allows you to input the tire circumference in mm or you can use the drop menu to select a preprogrammed size. (Best way to get your mm number is to measure mounted height and then do your conversion, always round up or down to a whole number. This might take a couple adjustments from that to get perfect at 60.)
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Press start and it should take a couple seconds to complete.
Once done back out to main page.

Cycle the key, at this point you can get all kinds of lights on the dash, so then you need to do the abs module.

Now select dodge/ram button, Ram 1500 or 2500 From drop down, ABS, then ABS Ate/Continental
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Connect then click on the icon at the bottom with the hood open
From the drop down select ABS iniatiliazation
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Read the instructions

View attachment 145951

Go back to the drop down and select static ECU initialization
Press start and wait to complete
Click on the check engine icon and clear faults
Then cycle key
Click back on the car icon
Select clearing Rolls Information from drop down, then start
After complete clear faults in the Body control module and the engine.
Cycle key
Once complete start your ram and take it for a spin, and check speed vs a gps. If your still off you can redo the process and adjust as needed.

This was performed on a 2018 Ram 2500 with version 2.1.4.0 on a android with OBDlink MX and a bypass cable

If anybody has noticed any differences on their vehicles or has any input to edit this let me know.

Thanks so much for the instructions. My 1st try at adjusting for tire diameter change resulted in loss of speedo function and the various dash lights. After reading your post and a lot of related posts I was able to go back and finish the change by doing the ABS initialization and removing the trouble codes and warnings (I did not have to recal the accel). Thanks again - I now have confidence to attempt the TPMS limit adjustments on my 2013 RAM.