Speedometer Calibration

[Shwagon]

I just went to 35" BFG t/A KO2 tires from stock. I want to re-calibrate my speedometer.

My dealership told me they can't calibrate the speedometers on 2021 HD models yet. Procal devices seem to be sold out. Any thoughts here guys?

Thanks in advance.

 

[SeppW]

I have read Alpha OBD will work with the bypass cable on MY21s.

 

[Adventurebound]

Have you tried looking for resellers for procal. It seems it's always out of stock on the AEV website but can be found elsewhere.

 

[CanRebel]

Not HD. But I changed Wheels/Tires on my 2021 Rebel.
Used AlfaOBD, ZAutomotive SGB module, OBDLink MX+
I used the windows version of AlfaOBD.

Had few issues, mostly user problems.

Biggest issue I had, when I entered the Circum. based on tire web sites.
It would disable my front and back sensors. Lowering the number tiny, and now it's all working.

On this forum, and few youtube video's said do ABS steps. Those steps don't 'seem' to do anything on this truck.
I had or have any faults.

 

[Graygoose]

see if Rough Country speedo recalibrate is updated for 21's.

 

[Roman2468]

If you have GPS it will automatically calibrate within a few hundred miles. I didn’t believe it either, but it did it both when I went to 35s and 37s. Confirmed it with 2 speedo apps before and after.

 

[olyelr]

If you have GPS it will automatically calibrate within a few hundred miles. I didn’t believe it either, but it did it both when I went to 35s and 37s. Confirmed it with 2 speedo apps before and after.

Thats the first i have heard of this. Seems wishful thinking for sure, but…

 

[Roman2468]

Well something, without my input, corrected my speedo for my 37s. I can driver down the highway at 70 and 2 separate speedo apps match what my trucks says within 1mph.

 

[ZLAYER]

Search this forum. There’s a lot of info. Ram Tazer is what I and many others use. You’ll find all the info on here.

 

[JRamirez]

Not HD. But I changed Wheels/Tires on my 2021 Rebel.
Used AlfaOBD, ZAutomotive SGB module, OBDLink MX+
I used the windows version of AlfaOBD.

Had few issues, mostly user problems.

Biggest issue I had, when I entered the Circum. based on tire web sites.
It would disable my front and back sensors. Lowering the number tiny, and now it's all working.

On this forum, and few youtube video's said do ABS steps. Those steps don't 'seem' to do anything on this truck.
I had or have any faults.

How did you fix it to get the front and back sensors working again....mine is doing the same

 

[CanRebel]

How did you fix it to get the front and back sensors working again....mine is doing the same

I put lower numbers over and over again, until I was as close as possible to what it should be, while making sure the sensors still worked.
Example, took the number that was there already, increased it by 5. saved it, waited. Checked if the sensor's worked.
Then did that process over and over again.

 

[JRamirez]

What do you mean lowered the numbers? I now have 35” tires….would you recalibrate it by inputting 34.5”….test it…..then 34”…then test it again etc until it works?

 

[CanRebel]

What do you mean lowered the numbers? I now have 35” tires….would you recalibrate it by inputting 34.5”….test it…..then 34”…then test it again etc until it works?

Sort of, I increased the numbers. Took value that was already there(default value before changing wheel/tires), slowly increased.
You could try it lowering the number as well.

I sent screen shots and logs to developer of alfaobd, he couldn't figure out why the sensors were failing either,
with no error codes.

 

[Xyleff]

If you have GPS it will automatically calibrate within a few hundred miles. I didn’t believe it either, but it did it both when I went to 35s and 37s. Confirmed it with 2 speedo apps before and after.

Interesting, how come mine doesn’t calibrate itself. Went up to 18” on 295/70 only and speedo is off by 3-4.

 

[olyelr]

Interesting, how come mine doesn’t calibrate itself. Went up to 18” on 295/70 only and speedo is off by 3-4.

Depends on what year your truck is maybe.

The speedo is off by a percentage….not a mph…might be off 3 or 4 mph at 60, but much less at 30.

 

[Xyleff]

Depends on what year your truck is maybe.

The speedo is off by a percentage….not a mph…might be off 3 or 4 mph at 60, but much less at 30.

Mine’s a ‘21 and doesn’t matter what speed, it’s a consistent 3-4 throughout with mine.

 

[olyelr]

Mine’s a ‘21 and doesn’t matter what speed, it’s a consistent 3-4 throughout with mine.

How are you checking it, with a speed app or something?

Check it at like 10 mph, then at 75 mph…there will be a difference. Changing from a stock 32” tire to a 35” tire is almost 9% larger tire, so thats how much your mph will be off (which the overall mpg number that it is off will change with different speed). Going to a 37” tire is like 13% larger.

Seems some people with the newer trucks are claiming all they had to do was drive it for a bit and it fixed itself….as in did not need a speedo recalibration tool.

 

[Grand Mesa]

.

 

[Xyleff]

How are you checking it, with a speed app or something?

Check it at like 10 mph, then at 75 mph…there will be a difference. Changing from a stock 32” tire to a 35” tire is almost 9% larger tire, so thats how much your mph will be off (which the overall mpg number that it is off will change with different speed). Going to a 37” tire is like 13% larger.

Seems some people with the newer trucks are claiming all they had to do was drive it for a bit and it fixed itself….as in did not need a speedo recalibration tool.

Running through traffic speed patrol radars and my radar. I’d say 2021 is fairly new but guess it’s not new enough to recalibrate itself lol

 

[olyelr]

Running through traffic speed patrol radars and my radar. I’d say 2021 is fairly new but guess it’s not new enough to recalibrate itself lol

Haaaaaa. Well it amazes me that some apparently can…i dont understand how it is even possible, but some say it happens for them.

U can also download a free speed app on your phone which is very accurate from what I can tell.