Speedometer Calibration?

[Batt4Christ]

Had a RC level kit installed Saturday, and upgraded tires to Wildpeak A/Tw3 in LT295 60-20. I'm pretty happy so far... BUT...

According to my calculations, the speedo is now approximately 5.9% off. My understanding is that this impacts the computer's calculations for a myriad of things, including stability and traction control, and several other operating parameters... not to mention maybe causing me to go just enough over the speed limit to get a ticket!

Anyway - Called stealership and was quoted $129 IF they even can do the flash. He said it depends on if the specific tire size is in the system. If it isn't, they cannot do the flash. (but I would still be on the hook for the diagnostic fee).

Spoke with Rough Country - and they say that their programmer is not compatible with trucks with Park Assist. According to sevral groups I've searched - it likely comes down to the same issue the dealer has to jugglle - if you program a size that doesn't fit in the existing profiles in the ECM options - then it will deactivate Park Assist...

Some have posted that they had success by changing in small increments until the ECM accepted the size input and kept Park Assist.

Anyone here played this game and have advice?

 

[Graygoose]

Dang, was gonna say RC

 

[Batt4Christ]

Orders the RC anyway- after update of software in it, I hooked everything up and updated the tire size. Went well and did not lose the Park Assist!

But, I did notice my Speedo was now off by nearly the same amount as before, but the other direction!

So yesterday (Friday) I connected again and adjusted tire size down 1” and Speedo is now less than 1mph off at 55. That’s as close as factory was.




Sent from my iPhone using Tapatalk Pro

 

[malquid]

I had no problem changing the circumference way down to accommodate my bigger tires using Alfaobd. It now matches the gps from 3 different apps.
I did go down in increments of 10 though, and and snuck up on it. I did not lose parking assist or have to recalibrate ABS.

 

[2021Ram3500]

Call AEV tech support and ask it they're module will do what you want. I used they're module to reprogram my new truck to my new tires. I used my Garmin GPS to compare speeds until I found the right setting to get the correct speed. Don't know about the Park Sense though. Worth a phone call right?