Tire size change alfaOBD

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tzr916

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You need to do the static ecu init., the longitudal sensor calibration AND clearing rolls.

Also need to go under engine > chrysler Powertech/Penntastar/Hemi and clear faults there to get rid of the CEL.

Looks like you are missing the step to clear the engine module at the end after the BCM.

Yep, looks like that was it! No more CEL.

Strange that the CEL did not happen at all the first time around, as I did NOT do the Engine module fault clear the first time. Oh well, now it's done. I thought I was up shtz creek there for a few...

Thanks so much!
 

257Ram

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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.)
View attachment 145954

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
View attachment 145953


Connect then click on the icon at the bottom with the hood open
From the drop down select ABS iniatiliazation
View attachment 145952

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.

I have 2017 Ram 2500 Laramie with 35X12.5X20 and selected the pre-select 35 X12.5X18 from the drop down and I am getting the correct speed now. No issues, just have to wait five minutes between each change to avoid issues. Thanks your instructions were on point
 

2018NightRam

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Anyone in the Los angeles / orange county area that'd be able to do this for me?
 

G. Mcpherson

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Going to be installing 295-70-18 tires on my 2018 ram 2500. Curious as to what MM setting is being used for accurate Speedometer readout. Going to use the Tire Size Calculator but want to see what would be more accurate.
 

CincyCuda68

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Going to be installing 295-70-18 tires on my 2018 ram 2500. Curious as to what MM setting is being used for accurate Speedometer readout. Going to use the Tire Size Calculator but want to see what would be more accurate.
Measure it top to bottom, use an online diameter to circumference calculator, then convert that to mm. I used an online calculator for that as well.
 

G. Mcpherson

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Thanks. Measure when mounted on the Truck? Might be more accurate also.
 

1500ram12

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Be prepared to adjust the tire size more than once. It took me a couple of tries to get it close. I'm off just about 1 mph (slow) right now. I'm running 35's which generally measure around 34.5" depending on manufacturer. I started with that and ended up just north of 33.75". I tested the GPS on my phone in my girlfriend's stock Silverado to make sure it was "accurate" before changing my tire size.


2018 2500 6.4L
 

malsup83

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I have 35's on mine and did this. i'd like to go to 37's after my leveling kit, too bad it doesn't go any higher.
 

1500ram12

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I have 35's on mine and did this. i'd like to go to 37's after my leveling kit, too bad it doesn't go any higher.

You can manually enter the tire size in millimeters


2018 2500 6.4L
 
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OP
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Redheadhunter21

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Yep 37's will be no problem, I know up to 40" tires has been successful using the "mm" box.
 

G. Mcpherson

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Just finished doing a tire size change for a friend and it was a complete success. Going to do mine when I get my tires next.
 

HTXRamExp

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Wondering if yall might be able to help me out, maybe point out where I went wrong since I haven't been successful with updating my tire size via AlfaOBD.

2019 Ram 1500 Classic Tradesman Express


AlfaOBD version 2.1.7.0
Nexus 7 Android version 6.0.1
OBDLink MX Bluetooth


Turn key to run
Plug OBDLink into OBD port
Open AlfaOBD app
Connect to OBDLink via BT
Select Dodge/Ram
Select Ram 1500 DS/DX
Select body computer
Select body computer MY2016-17 powernet
(Have also tried w/ MY2013-17 powernet)
Select connect
Select vehicle w/ hood up icon
Select program tire size from drop down
Manually enter 2720mm (nitto 275/65r20 Terra g2)
Select start
Wait until confirmation of entered circumference
Back out to main AlfaOBD screen
Turn key to off
Wait ~1min
Turn key to run
(No dash warning lights except for check engine light)
Select ABS from drop down menu
Select ABS Ate/Continental from drop down menu
Select connect
(Once connected - abs dash light, brake dash light, service electronic braking system message)
Select car w/ hood up icon
Select ABS initialization
Read instructions
Select static ECU initialization from drop down
Select start, wait for complete
Select check engine icon
(no faults reported)
Select clear faults anyways
Turn key to off
Turn key to run
Select car w/ hood up icon
Select clearing rolls information
Select start
Failed. Service not supported in Active Diagnostic Session.

I've checked the BCM/Engine for fault codes, none present.
I've forced closed the app. Let the truck sleep for a bit, reconnect everything and try again. Still error out in the same spot.
I've tried waiting a few days inbetween attempts and still no luck.

Attached is a screen shot of my vehicle config., highlighting the dynamic tire circumference. The only odd thing about this is the second entry for dynamic tire circumference does not match the first and is quite a bit larger. Unsure if this is indicative of something that is incorrect.

Thanks.

Edit: I checked in shared google drive for shared BCM config. files and the ones posted match the 2640 and 65535 entries for dynamic tire circumference.

Dynamic Tire Circumference Screenshot.jpg
 
Last edited:

1500ram12

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Wondering if yall might be able to help me out, maybe point out where I went wrong since I haven't been successful with updating my tire size via AlfaOBD.

2019 Ram 1500 Classic Tradesman Express


AlfaOBD version 2.1.7.0
Nexus 7 Android version 6.0.1
OBDLink MX Bluetooth


Turn key to run
Plug OBDLink into OBD port
Open AlfaOBD app
Connect to OBDLink via BT
Select Dodge/Ram
Select Ram 1500 DS/DX
Select body computer
Select body computer MY2016-17 powernet
(Have also tried w/ MY2013-17 powernet)
Select connect
Select vehicle w/ hood open up icon
Select program tire size from drop down
Manually enter 2720mm (nitto 275/65r20 Terra g2)
Select start
Wait until confirmation of entered circumference
Back out to main AlfaOBD screen
Turn key to off
Wait ~1min
Turn key to run
(No dash warning lights except for check engine light)
Select ABS from drop down menu
Select ABS Ate/Continental from drop down menu
Select connect
(Once connected - abs dash light, brake dash light, service electronic braking system message)
Select car w/ good icon
Select ABS initialization
Read instructions
Select static ECU initialization from drop down
Select start, wait for complete
Select check engine icon
(no faults reported)
Select clear faults anyways
Turn key to off
Turn key to run
Select car w/ good up icon
Select clearing rolls information
Select start
Failed. Service not supported in Active Diagnostic Session.

I've checked the BCM/Engine for fault codes, none present.
I've forced closed the app. Let the truck sleep for a bit, reconnect everything and try again. Still error out in the same spot.
I've tried waiting a few days inbetween attempts and still no luck.

Attached is a screen shot of my vehicle config., highlighting the dynamic tire circumference. The only odd thing about this is the second entry for dynamic tire circumference does not match the first and is quite a bit larger. Unsure if this is indicative of something that is incorrect.

Thanks.

View attachment 170018

I'm not sure if anyone has done this on a 19 classic although nothing should really be different. For whatever reason the tire change won't show up in the bcm logs.

Have you tried to go for a drive and verify via GPS that it either has changed or hasn't?


2018 2500 6.4L
 

HTXRamExp

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I'm not sure if anyone has done this on a 19 classic although nothing should really be different. For whatever reason the tire change won't show up in the bcm logs.

Have you tried to go for a drive and verify via GPS that it either has changed or hasn't?


2018 2500 6.4L

Driving around, I'm within ~1 mph, but my tire size only increased from 33" to 34.09" according to the wrangler and nitto websites for inflated tire ODs, so even w/o updating the tire size, I'd only be off ~2mph according to an online tire comparison chart.
 

HTXRamExp

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It's mainly my OCD/odometer tracking and the fact that I seem to not be able to complete the procedure is what is bothering me, versus the slight variance in mph.
 

HTXRamExp

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While going through AlfaOBD, changing some other settings, I came across "VehConfig 4-Dynamic Tire Circumference (All or Rear) in the BCM>Body Computer>Car Configuration Change. All it has is a box to manually enter a circumference. A hint is given stating that if the ABS throws faults after changing the tire size, run ABS initialization procedure available in the ABS diagnostics.

Based on the successful posts throughout this thread, modifying this parameter isn't required to change tires sizes, but I wonder if updating it here would change the value stated in the config file?
 

1500ram12

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While going through AlfaOBD, changing some other settings, I came across "VehConfig 4-Dynamic Tire Circumference (All or Rear) in the BCM>Body Computer>Car Configuration Change. All it has is a box to manually enter a circumference. A hint is given stating that if the ABS throws faults after changing the tire size, run ABS initialization procedure available in the ABS diagnostics.

Based on the successful posts throughout this thread, modifying this parameter isn't required to change tires sizes, but I wonder if updating it here would change the value stated in the config file?

I tried it when I updated my tire size recently and it still didn't change anything in the config files. It's possible that it's just something that can't be charged or something alphaobd can't change yet. It was recently added but he may not have the code correct to make the changes in the bcm to show the new tire size.


2018 2500 6.4L
 

drprymer

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So I just got my obd adapter (cheap amazon one) Went through the steps here and to my surprise I did everything right the first time and was dead on with the speed. It used to read 11mph over what i was actually running and it was annoying hitting the speed limiter on the interstate with a Prius passing you. I cant wait to dig more into this and see what I can do!


** Also will this change my shift points? When I bought the truck it was lifted on 35s and I actually ran into the previous owner and he said he calibrated it with a hypertech before. Ever since I lowered it and change the tire size it seemed to shift differently. Im hoping this change brings it back to how it was before
 
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CincyCuda68

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So I just got my obd adapter (cheap amazon one) Went through the steps here and to my surprise I did everything right the first time and was dead on with the speed. It used to read 11mph over what i was actually running and it was annoying hitting the speed limiter on the interstate with a Prius passing you. I cant wait to dig more into this and see what I can do!


** Also will this change my shift points? When I bought the truck it was lifted on 35s and I actually ran into the previous owner and he said he calibrated it with a hypertech before. Ever since I lowered it and change the tire size it seemed to shift differently. Im hoping this change brings it back to how it was before
Damn 11 mph is a huge difference, shouldn’t have been that far off. When I switched from stock to 35’s I was off 2 mph.
Anyway, Alfa doesn’t change shift points but having the speedo accurate will.
 
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