JSCAN Issues- Solved

[Bad Luck Bill]

I finally got my lift, wheels, and tires installed. (37x12.5x17 and it measures 36.75) I am using the recommended BT adapter and security bypass cable to connect. I programmed my tire size to 36.75 and my speedo is of significantly at 65. I have changed it off and on over the past week and I am now at 38in and I am reading 65 on the Speedometer but am only doing 60mph. Anyone have had the same issues?

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[Mr._Bill]

I finally got my lift, wheels, and tires installed. (37x12.5x17 and it measures 36.75) I am using the recommended BT adapter and security bypass cable to connect. I programmed my tire size to 36.75 and my speedo is of significantly at 65. I have changed it off and on over the past week and I am now at 38in and I am reading 65 on the Speedometer but am only doing 60mph. Anyone have had the same issues?

There are other threads, this is a common issue, regardless of the programmer used to do the update. Start by measuring from the center of the wheel to the ground and doubling. The size needed to be entered is commonly less than the manufacturer listed size.

 

[Bad Luck Bill]

There are other threads, this is a common issue, regardless of the programmer used to do the update. Start by measuring from the center of the wheel to the ground and doubling. The size needed to be entered is commonly less than the manufacturer listed size.

I will try it, but it seems the larger I go the closer it gets to correct at highway speeds.

 

[Mr._Bill]

I will try it, but it seems the larger I go the closer it gets to correct at highway speeds.

It will take several tries, it may need to be smaller, and it might need to go larger. If using the phone GPS to test, do not connect the USB cable to the truck (a power only connection to the 12v port is okay).

 

[CivilJeep]

Updated my tire size recently, and the JSCAN app had a pop up saying to turn off the vehicle and close the drivers door for 5 minutes to complete the adaptation. I assume you saw this pop up and have performed this step?

 

[Bad Luck Bill]

Updated my tire size recently, and the JSCAN app had a pop up saying to turn off the vehicle and close the drivers door for 5 minutes to complete the adaptation. I assume you saw this pop up and have performed this step?

Yep and even the nice folk's a JSCAN actually said to give it a few hours. I reset it to factory earlier today and I changed it to the measurements I actually measured and will check again tomorrow.

 

[CivilJeep]

Yep and even the nice folk's a JSCAN actually said to give it a few hours. I reset it to factory earlier today and I changed it to the measurements I actually measured and will check again tomorrow.

Let us know how it turns out. My tire size adaptation was spot on to GPS, but when I tried the ESS disable adaptation, it didn't work at all. I found the JSCAN support to be lackluster.

 

[Bad Luck Bill]

Let us know how it turns out. My tire size adaptation was spot on to GPS, but when I tried the ESS disable adaptation, it didn't work at all. I found the JSCAN support to be lackluster.

Will do, I believe I have been going the wrong direction in my thought process by raising the size vs reducing size.

 

[jeep671]

I had a similar challenge. Obviously, I consulted YouTube reviews, Jscan FB Groups, and https://jscan-docs.readthedocs.io/

I have Toyo Open Country MT 37x12.5R17 running at 30psi. The tires measured as follows:
Front-Driver: 36 1/2"
Front-Passenger: 36 7/8"
Rear - Driver: 36 13/16"
Rear - Passenger: 36 7/8"

I set the tire measurements closest to the 1/4" as per the instructions. It took me awhile to get the speed calibrated using Waze, Google Maps, and following a vehicle set to a specific cruise control speed.

I kept adjusting the tire sizes downward within the app and then register it with the Gladiator computer. The final tire size where the actual speed matched with the speedometer was at 34.5". I was quite surprised at the disparity between actual tire size and setting that had to be entered to calibrate the accurate speed.

I did inquire with Jscan with FB Instant Messenger and he was quick considering I am in the opposite side of the world. He is in Poland, while I am in Guam.

He was quite surprised with the disparity as well. He acknowledged the difference and stated that "the factory speedo is calibrated to show higher speed than you really go. Setting smaller tire offsets that and bigger the tire, the bigger the difference."

 

[Bad Luck Bill]

Yep, I was going the wrong direction. I was able to use the measurements on the front tires and I set it last night. This morning I am only 1mph off at 65. Still going to tinker with it , but it now acceptable for long drives. Thank you guys for the help.

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