Tire size change alfaOBD

[RockyAEV]

Guess it won’t hurt to give one or two more tries to get it exact haha thanks guys for the input it has been very helpful. I know without the original write up I would have panicked...because I would have changed the tire size and then all of the bells and whistles would have come on...without the steps of how to go through the ABS fix!


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[dwalk19]

Hey guys, i just attempted to change tire size before i saw this forum, i just got the alphaobd and have turned 9n global down so far

I just attempted to change tire size before seering this post, i selected 35" tires at bottom of list, turned off truck and turned back on and got

1) park sense off
2)service ABS
3)check engine & abs light

I then changed back to stock 265 size because i figured i "broke" something,,, i hacent been back out to check and see if messages & lights will still be on (i'm assume they will even though i changed it back) but now know its normal i think,, but when i need to
re-iniate my abs, how do i know which abs to choose



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[keepemrollin14]

Hey guys, i just attempted to change tire size before i saw this forum, i just got the alphaobd and have turned 9n global down so far

I just attempted to change tire size before seering this post, i selected 35" tires at bottom of list, turned off truck and turned back on and got

1) park sense off
2)service ABS
3)check engine & abs light

I then changed back to stock 265 size because i figured i "broke" something,,, i hacent been back out to check and see if messages & lights will still be on (i'm assume they will even though i changed it back) but now know its normal i think,, but when i need to
re-iniate my abs, how do i know which abs to choose

I did this on my truck go to around 6:00 in video and I walk through it.


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[WTM75]

Guess it won’t hurt to give one or two more tries to get it exact haha thanks guys for the input it has been very helpful. I know without the original write up I would have panicked...because I would have changed the tire size and then all of the bells and whistles would have come on...without the steps of how to go through the ABS fix!


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When I changed mine from 20s to 17s, I played with the mm a few times because the tire I have was not listed. Then I just chose the tire that is stock on the Rebel and it was right on. I was/am using the stock Rebel size tire but a different brand(Falken). My speedo and gps are dead on out to 75mph.

 

[RockyAEV]

When I changed mine from 20s to 17s, I played with the mm a few times because the tire I have was not listed. Then I just chose the tire that is stock on the Rebel and it was right on. I was/am using the stock Rebel size tire but a different brand(Falken). My speedo and gps are dead on out to 75mph.

Thats awesome! I have been playing around with this for days now and have changed it somewhere around 15 times and I am still not dead on. I remain at 75mph on the dash, the actual speed is 74. That is close enough for me, lower speeds are more accurate...60 and below are dead on. I know that all speedometers have a slight tolerance that they could be out and most likely all of my vehicles that I have had before were probably off by a slight margin but I never tested it lol


2018 Ram 2500 Tradesman
6.7L, G56

 

[WTM75]

Thats awesome! I have been playing around with this for days now and have changed it somewhere around 15 times and I am still not dead on. I remain at 75mph on the dash, the actual speed is 74. That is close enough for me, lower speeds are more accurate...60 and below are dead on. I know that all speedometers have a slight tolerance that they could be out and most likely all of my vehicles that I have had before were probably off by a slight margin but I never tested it lol


2018 Ram 2500 Tradesman
6.7L, G56

Try one of the preloaded brands that match your size, maybe it will work for you too.

 

[RockyAEV]

Try one of the preloaded brands that match your size, maybe it will work for you too.

Thus far I have not found one that matches exactly, it’s either one size taller or one size smaller [emoji2369] I guess over the next few weeks I’ll change it one number at a time until i find that magical number lol


2018 Ram 2500 Tradesman
6.7L, G56

 

[keepemrollin14]

One thing I wanted to say was I thought I remembered reading somewhere that your speedo can actually be up to a max of 3% off which at 70mph would be like 2mph. On another note have you taken the measurement of your tire mounted on the truck with a level at the top and measuring down to the ground? Once you obtain that then convert to mm and input that into the truck. I’ve done it for 2 different size tires, 33x12.50R20 and 35x12.50R20 and both have been spot on at 60 and 75mph.


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[G. Mcpherson]

See Post #132

 

[RockyAEV]

See Post #132

Man I should have followed your instructions days ago! I measured, got my circumstance, converted to millimeter and bam I am spot on till 72...at 75 I am at 74.6 can’t argue with that at all!


2018 Ram 2500 Tradesman
6.7L, G56

 

[G. Mcpherson]

What was your final Measurement. MM

 

[RockyAEV]

What was your final Measurement. MM

It was way off from what all the numbers I found online when I put in the tire size.

Online search size in MM= 2718
Level + tape, converted into MM= 2673


2018 Ram 2500 Tradesman
6.7L, G56

 

[Don_T]

I have 295/65R20 tires on my truck now. I measured the tires 34” with the weight of the truck on them. The circumference came out to 2713. I put that in AlphaOBD and now the speedometer is right on at 60 MPH.

 

[Chris Kyle]

So, my OBDLink MX+ arrived yesterday and I fiddled around with it in the afternoon. It took a little trial and error; but eventually it was connecting to the truck and to AlfaOBD.

When I got home, I fired up the laptop and connected to the truck. While the directions are specifically for the Android version, the Windows version was kind of straight forward and pretty similar. I measured my 35x11.50 Ridge Grapplers to right around 33.75", and using the online calculator, came up with 2,694mm.

I first Read the Sys ID and saved it as a txt file, then walked through the steps to set the tire size. It all worked fine. After setting the tire size, I went through the ABS Initialization steps; which ended up being running the Static ECU Initialization and Clearing the Rolls. I checked for body, engine and abs faults and had none. I went through the clearing process anyways.

Took the truck out for a spin around the neighborhood and could immediately tell it was acting more normal than before. The fuel economy was reporting closer to normal and ECO was engaging more frequently, as it used to do.

I compared speed this morning against my Garmin and it was pretty spot on from 20-50mph. I haven't gotten up to 60mph or higher yet; but I think it will be darn close.

 

[kylant]

quick questions:
does alfa automatically update software? and do I need to update the firmware on my obdlink mx?

 

[superjoe83]

quick questions:
does alfa automatically update software? and do I need to update the firmware on my obdlink mx?

you can download "OBDlink" which is made by the manufacture of the obdlink mx, and that app will update the tool, also it has some good features in it too, i use it in my '18 3500 cummins to monitor exhaust temps and if its in a regen or not.

AlfaOBD will update itself whenever a update is ready, just like any other app

 

[kylant]

you can download "OBDlink" which is made by the manufacture of the obdlink mx, and that app will update the tool, also it has some good features in it too, i use it in my '18 3500 cummins to monitor exhaust temps and if its in a regen or not.

AlfaOBD will update itself whenever a update is ready, just like any other app

is it necessary to update the tool? last time I used it, it worked fine

 

[kylant]

another question:
my 285/75-18 listed size is 35.1"

I have measured my tire height with the level on top of the tire method. Front tires measure 33.5", rear tires measure 33.75"

which of the 2 measured heights should I convert to mm and use for the input?
thanks

 

[G. Mcpherson]

Start with 33.5. Check it with a GPS and Go from there.

 

[kylant]

ok, pulled the trigger and got it done. was a little nerveracked at first.
went with the measured height of 33.75" on the truck, 285/75-18. converted to a circumference of 2693.
speedo was very close, I would say anywhere from 1/2-1mph fast.

i went home and corrected to 2691. speedo was still fast, but gps seemed to respond faster more inline with the speedo.

i corrected to 2689 for the last time. the speedo and gps were pretty darn accurate and close to each other. the speedo still would read a touch faster for a moment, then the gps would respond.

i think i am done adjusting for now.

i may reduce another 2mm and see if that makes it dead accurate.

thanks for all the info