Needing Speedo Calibration Assistance

[Rosser]

New to the Ram trucks and needing help on calibration for the speedo. I’m upgrading to 35” tires on my 2016 2500 6.4 come spring and found my speedo will be off by like 3.5 mph. Looking into the OBDLink MX+ since you can use iOS. Now I’m confused on do I run Alpha app with the MX+ or the OBDLink app with the MX+?

Like like to use my iPhone 11 to setup the speedo and use it when in the truck down the road.

 

[jawzs2]

AlfaOBD does not work on IOS, Android or Windows only. The OBDLink app won't change tire size

 

[2012RAM1500RT]

I put 1 in. taller tires on mine which made the speedometer 3 MPH slower, I was able to correct it with ALFAOBD by changing my gear ratio from a 4.10 to a 3.91. Worked great.

 

[Rosser]

Does the Alpha change the tire size?

I do have a old taplet that is Android if Alpha is the way to go

 

[2012RAM1500RT]

Does the Alpha change the tire size?

I do have a old taplet that is Android if Alpha is the way to go

I'm sure it does. I don't remember why I went the gear ratio route but I guess either way will work but I know the way I did it worked so that's the only one I can guarantee.

 

[John Jensen]

I put 1 in. taller tires on mine which made the speedometer 3 MPH slower, I was able to correct it with ALFAOBD by changing my gear ratio from a 4.10 to a 3.91. Worked great.

When you did that you may have changed things other than the speedometer. You probably changed shift points and who knows what else. Is the odometer still corect? I believe your method of making the speedometer correct was coincidental.

Alfa can change tire diameter size to whatever you want. I suggest you undo and redo correctly.

 

[2012RAM1500RT]

When you did that you may have changed things other than the speedometer. You probably changed shift points and who knows what else. Is the odometer still corect? I believe your method of making the speedometer correct was coincidental.

Alfa can change tire diameter size to whatever you want. I suggest you undo and redo correctly.

I'll look into it. Yes the odometer seems correct, haven't seen where it changed anything in the wrong way but I'll recheck. Thanks

 

[John Jensen]

I'll look into it. Yes the odometer seems correct, haven't seen where it changed anything in the wrong way but I'll recheck. Thanks

I could be wrong as I have no experience with it. It's what I've read and what others have reported.

It's good to recheck, let us know what you find.

 

[2012RAM1500RT]

I could be wrong as I have no experience with it. It's what I've read and what others have reported.

It's good to recheck, let us know what you find.

I have no issue with finding out if I done something right or not. Thanks

 

[retired]

generally if you change your gear ratio without physically changing your gears you will go into limp mode. Very strange that this worked without going into limp mode.

 

[2012RAM1500RT]

generally if you change your gear ratio without physically changing your gears you will go into limp mode. Very strange that this worked without going into limp mode.

I've driven it for about 5000 miles since I changed it but will change it this weekend to see if anything does different.