AlfaOBD

[kd908070]

I changed my tires and wheels on my 2020 Lonestar. When I tried updating the size on alfaobd it caused my speedometer to be over by 2 mph. I've tried to go back in numerous times to change the size around to correct the speedometer with no avail. Also my front and rear park sensors went unavailable. Can any one help get things corrected?

OEM tires were 275/65/18
Changed to LT285/55/20

You don't have to remember the old value. Just figure out the correct number of the current circumference . Very easy to do.
Right at the center of your wheel, measure from the bottom of your wheel to the top of your wheel in mm. Very important that you use mm to measure. Then, take the value times with 3.14 (pi) give you the new circumference value. Note: pi is 3.14.
Example: I measured my wheel as shown in the photo, I got 820mm. Take 820mm x 3.14 = 2574.8 mm >>> round up to 2575mm. I enter 2575 to Alfa.

 

[Idahoktm]

You don't have to remember the old value. Just figure out the correct number of the current circumference . Very easy to do.
Right at the center of your wheel, measure from the bottom of your wheel to the top of your wheel in mm. Very important that you use mm to measure. Then, take the value times with 3.14 (pi) give you the new circumference value. Note: pi is 3.14.
Example: I measured my wheel as shown in the photo, I got 820mm. Take 820mm x 3.14 = 2574.8 mm >>> round up to 2575mm. I enter 2575 to Alfa.
View attachment 111985 View attachment 111986

Even when I figured out my circumference, my speedometer was still off by 1 mph. I made a WAG and came up with a number that was perfect. I figured if he entered the OEM circumference, his speedometer would be accurate without having to make multiple adjustments.

 

[c3k]

Something to be aware of...
Static/book circumference is different than "dynamic" or "in use" circumference. The difference is the flex due to the weight on the tire.

For example, I added Falken AT3Ws in 275/65 R20. If you do the math, the circumference is:
((275mm * .65) x 2 + (20in x 25.4mm/in)) x pi = 2,719mm

But, the values for my tire state it takes 611 revolutions per mile, so the ACTUAL circumference is:
5,280 ft/mi / 611 revs/mi = 8.6416 ft/rev. Using that, 8.6416 ft/rev x 12in/ft x 25.4mm/ft = 2,634mm per revolution

That's just over 3% "loss" of circumference in the actual operation.

I used AlfaOBD and the calibrated to the 2,634mm circumference. Using a GPS, my speedometer had zero error up to 82 mph.

Look at your tire manufacturer's website (or a large distributor like Discount Tire or TireRack) to get the revs per mile figure.

 

[kd908070]

Something to be aware of...
Static/book circumference is different than "dynamic" or "in use" circumference. The difference is the flex due to the weight on the tire.

For example, I added Falken AT3Ws in 275/65 R20. If you do the math, the circumference is:
((275mm * .65) x 2 + (20in x 25.4mm/in)) x pi = 2,719mm

But, the values for my tire state it takes 611 revolutions per mile, so the ACTUAL circumference is:
5,280 ft/mi / 611 revs/mi = 8.6416 ft/rev. Using that, 8.6416 ft/rev x 12in/ft x 25.4mm/ft = 2,634mm per revolution

That's just over 3% "loss" of circumference in the actual operation.

I used AlfaOBD and the calibrated to the 2,634mm circumference. Using a GPS, my speedometer had zero error up to 82 mph.

Look at your tire manufacturer's website (or a large distributor like Discount Tire or TireRack) to get the revs per mile figure.

I understand that, but the number on paper doesn't match up with the physical measure in my case too.
I have the Falken Wildpeak in 285/60R20. If i do the math on paper my circumference is ((285mm * .60) x 2 + (20in x 25.4mm/in)) x 3.14 = 2669mm, but as I shown in my photo earlier, my real circumference is 2575mm.
We can use the rev per mile to figure out the circumference as you showed or measure the physical wheel as I did, just don't use the size of the tires on paper.

 

[c3k]

I understand that, but the number on paper doesn't match up with the physical measure in my case too.
I have the Falken Wildpeak in 285/60R20. If i do the math on paper my circumference is ((285mm * .60) x 2 + (20in x 25.4mm/in)) x 3.14 = 2669mm, but as I shown in my photo earlier, my real circumference is 2575mm.
We can use the rev per mile to figure out the circumference as you showed or measure the physical wheel as I did, just don't use the size of the tires on paper.

I just went here: https://www.falkentire.com/tires/light-truck-suv-cuv-tires/wildpeaka/t3w-tire

Looking up your tire, Falken says it has: 622 Revs Per Mile.

A little maths...and we get 2,587mm as the value you should use.

That 12mm difference from your number means 1/2" per tire rotation. That's pretty darn close to your measured number. (Actual measurement may be better, since your pressure may differ from what the factory assumes. But, it'll get the OP onto the right page...) (1/2" per rev difference means ~ 311 inches per mile, or 99.5% of your value. At 75mph, that'd be 74.6mph. So...darn good.)

Either way, it's always a little less than just using the tire size plus rim.

 

[grimloktt]

Does anyone know is there a way to change USB ports to power off with vehicle? Thnx

Sent from my SM-N986U1 using Tapatalk

 

[vincentw56]

Does anyone know is there a way to change USB ports to power off with vehicle? Thnx

Sent from my SM-N986U1 using Tapatalk

They do, it just takes a little longer after you shutoff the truck.

 

[grimloktt]

They do, it just takes a little longer after you shutoff the truck.

Yes. I read they shut off after about an hour. I wonder if I can make it sooner...

Sent from my SM-N986U1 using Tapatalk

 

[Brutal_HO]

On the HD's some ports have a selectable fuse for BAT or IGN. You might check the PDC cover or OM.

 

[brian42]

I don't think the USB power is "adjustable".

For the 1500 the only port I know that's switchable is the 12V port on the top of the dash - hot (battery) or switched (ignition).

From the Owner's Manual:

 

[Idahoktm]

I just tried to disable the seatbelt chime on my 2021 Laramie with AlfaOBD. It did not work. It said something about not being able to recalibrate the odometer...wish I would have done a screenshot. I tried it twice with the same message. I used the seatbelt latch/unlatch 3 times procedure and that worked, so no big deal.

 

[Whoa_Ram]

Hey guys, still new to alfaobd. I have a question. I read that it is a good idea to upload your status log to google drive, but every time I do it, it comes back blank. Any idea why that is?
I want to change my tire size as it is off my a little and I want to have my log of my truck so I don't mess up anything. Thanks

 

[kd908070]

Hey guys, still new to alfaobd. I have a question. I read that it is a good idea to upload your status log to google drive, but every time I do it, it comes back blank. Any idea why that is?
I want to change my tire size as it is off my a little and I want to have my log of my truck so I don't mess up anything. Thanks

You should download the Log to your phone or PC then upload it manually later.

 

[Jimmy07]

Hey guys, still new to alfaobd. I have a question. I read that it is a good idea to upload your status log to google drive, but every time I do it, it comes back blank. Any idea why that is?
I want to change my tire size as it is off my a little and I want to have my log of my truck so I don't mess up anything. Thanks

You need to go into faults/status tab (battery icon in lower right on Android version) and read the system ID first. Also, new for the recent update, in active diagnostics just below car configuration change, you can create a backup file of your current configuration, and use it as a full automatic restore point in case you screw something up.

 

[Whoa_Ram]

You need to go into faults/status tab (battery icon in lower right on Android version) and read the system ID first. Also, new for the recent update, in active diagnostics just below car configuration change, you can create a backup file of your current configuration, and use it as a full automatic restore point in case you screw something up.

Awesome. I knew I was missing something. Jimmy while you are here can you help me out in one thing. When I added the blind side mirrors and went in and changed the features so the buttons would show up in my 12" display the buttons for the BSM trailer features never showed up. Do you know what needs to be checked so they appear? I towed a trailer the other day and the BSM read my trailer, but the actually setting in the display aren't there.

 

[Jimmy07]

Awesome. I knew I was missing something. Jimmy while you are here can you help me out in one thing. When I added the blind side mirrors and went in and changed the features so the buttons would show up in my 12" display the buttons for the BSM trailer features never showed up. Do you know what needs to be checked so they appear? I towed a trailer the other day and the BSM read my trailer, but the actually setting in the display aren't there.

CustSetMenu 3: Trailer Length Blind Spot Enable/Disable CSM Present- YES

 

[Whoa_Ram]

CustSetMenu 3: Trailer Length Blind Spot Enable/Disable CSM Present- YES

well dang I've done everything I needed to do with alfa for the time being. Thank you very much guys!

 

[Whoa_Ram]

I’m assuming this doesn’t work for our trucks?

Passive Entry Unlock All Doors or Approach Door: Not enabled

 

[Crf450r23]

Does anyone know if there is a way to adjust the acceleration rate of the Adaptive Cruise Control (ACC) system on a 2020 2500 Laramie 2 6.7 with Alfaobd by chance? I’m pretty sure a Prius would smoke me off the line right now!!! Lol. Also, is there a way to increase the stop time above 2 seconds before it kicks you out of ACC at a stop light? Both of which are very annoying!! First world problems for sure!!!

 

[vincentw56]

Does anyone know if there is a way to adjust the acceleration rate of the Adaptive Cruise Control (ACC) system on a 2020 2500 Laramie 2 6.7 with Alfaobd by chance? I’m pretty sure a Prius would smoke me off the line right now!!! Lol. Also, is there a way to increase the stop time above 2 seconds before it kicks you out of ACC at a stop light? Both of which are very annoying!! First world problems for sure!!!

Not possible with AlfaODB right now. Not sure if we will ever be able to modify it. Just press the gas until you are up to where you want to or ready for it to take over. That's what I do.