Do I need to program Speedo

[Rodger1966]

I have 35s on mine and started at 2710 and park sense went out. Tried 2700 and park sense came back, but speedo was still off. 2670 ended up working for park sense and is pretty much right on with the gps for speed now.

I went with a 35/12.50-18 that existed within the Alfa app, it put the size at 2799. Speedo reads 75, GPS 73ish. I will try the number you suggested and see.

 

[skyhawk42]

I went with a 35/12.50-18 that existed within the Alfa app, it put the size at 2799. Speedo reads 75, GPS 73ish. I will try the number you suggested and see.

Make sure when you check with the gps if you use your phone it’s not connected to the truck in anyway. If it is it will be almost right on to what the truck says. Once it’s not connected you can see the real difference

 

[HSKR R/T]

I wanna say 35". Here's your size. 35" should do it

View attachment 164436

35" tires don't measure 35" diameter. I just did a 4th gen. Ended on 2650mm to make speedometer accurate to GPS. My truck, using my TazerDT, I am at 34.7" to make speedo accurate, and park sense is still working

 

[John Jensen]

Make sure when you check with the gps if you use your phone it’s not connected to the truck in anyway. If it is it will be almost right on to what the truck says. Once it’s not connected you can see the real difference

What do you mean by "connected to the truck in anyway"?
I test with a Garmin GPS and my phone. The phone is powered by the truck's USB port. The phone and the Garmin report the same data. I have never experienced what you describe, don't think that can happen.

 

[John Jensen]

35" tires don't measure 35" diameter. I just did a 4th gen. Ended on 2650mm to make speedometer accurate to GPS. My truck, using my TazerDT, I am at 34.7" to make speedo accurate, and park sense is still working

To add to what you say, 35" tires of different make tires may measure different as well. They may not all have the same rpm rating.

 

[HSKR R/T]

What do you mean by "connected to the truck in anyway"?
I test with a Garmin GPS and my phone. The phone is powered by the truck's USB port. The phone and the Garmin report the same data. I have never experienced what you describe, don't think that can happen.

Depends on the app being used for GPS speed, and if you are connected using Android auto or Carplay.

 

[skyhawk42]

What do you mean by "connected to the truck in anyway"?
I test with a Garmin GPS and my phone. The phone is powered by the truck's USB port. The phone and the Garmin report the same data. I have never experienced what you describe, don't think that can happen.

Mine doesn’t read the correct speed on the phone if the CarPlay is connected. The speedo reads according to how I programmed it, the phone reads the gps when not connected to the CarPlay, but for whatever reason if the phone connects to CarPlay the speedo works, but the Waze app shows the wrong speed and the map freaks out

 

[John Jensen]

Depends on the app being used for GPS speed, and if you are connected using Android auto or Carplay.

Mine doesn’t read the correct speed on the phone if the CarPlay is connected. The speedo reads according to how I programmed it, the phone reads the gps when not connected to the CarPlay, but for whatever reason if the phone connects to CarPlay the speedo works, but the Waze app shows the wrong speed and the map freaks out

Gotcha. I wouldn't trust any phone app while connected to CarPlay.
I use a phone speedo app, I have three. The one I use the most is GPS Speedometer by Cool Niks. All three of my speedo apps mirror what the Garmin GPS is sayin for speed and distance, have never seen a variance.

 

[theblet]

IIRC when your phone is connected to the truck with usb, your gps app can use the trucks mph reading, instead of it’s own.

 

[John Jensen]

IIRC when your phone is connected to the truck with usb, your gps app can use the trucks mph reading, instead of it’s own.

Are you sure? I don't think the truck USB can input any truck data into the phone, I need some proof! I do know that when my phone is plugged into the truck's USB port and using its Speedometer app, the app pulls data from the GPS satellites in the sky to readout speed and distance, definitely not the truck's mph reading, I'm now using the truck's USB for a wireless charging phone mount, with the phone in that phone mount it's impossible for the truck to input data.

 

[theblet]

Are you sure? I don't think the truck USB can input any truck data into the phone, I need some proof! I do know that when my phone is plugged into the truck's USB port and using its Speedometer app, the app pulls data from the GPS satellites in the sky to readout speed and distance, definitely not the truck's mph reading, I'm now using the truck's USB for a wireless charging phone mount, with the phone in that phone mount it's impossible for the truck to input data.

Just something I read awhile back. No proof.

 

[HSKR R/T]

Are you sure? I don't think the truck USB can input any truck data into the phone, I need some proof! I do know that when my phone is plugged into the truck's USB port and using its Speedometer app, the app pulls data from the GPS satellites in the sky to readout speed and distance, definitely not the truck's mph reading, I'm now using the truck's USB for a wireless charging phone mount, with the phone in that phone mount it's impossible for the truck to input data.

Many different people, on this forum and Facebook groups, have reported similar experiences with having the phone plugged in using carplay or Android auto. The truck has to be able to send data to the phone or voice to text would never work.

 

[John Jensen]

Many different people, on this forum and Facebook groups, have reported similar experiences with having the phone plugged in using carplay or Android auto. The truck has to be able to send data to the phone or voice to text would never work.

Yes, as discussed in posts #26 & 28.
I was talking about a phone plugged into a truck USB port.

 

[HSKR R/T]

Yes, as discussed in posts #26 & 28.
I was talking about a phone plugged into a truck USB port.

That's how Android Auto and Carplay work

 

[John Jensen]

That's how Android Auto and Carplay work

We all know that.
theblet and I have been talking about using a GPS app, mainly the Speedometer app, not Carplay.

 

[Darksteel165]

We all know that.
theblet and I have been talking about using a GPS app, mainly the Speedometer app, not Carplay.

You don't understand what is going on.
Carplay just means your car is connected to your truck and sharing data, you can open apps while Carplay is connected.

The problem is not the app, or kind of app you use. It's about how you are or are not connected to your truck.
2022 and above also use wireless Carplay also.

 

[HSKR R/T]

We all know that.
theblet and I have been talking about using a GPS app, mainly the Speedometer app, not Carplay.

Carplay isn't an app, and if plugged in through USB with Carplay running, some apps, for some reason, will default to vehicle speed sensor. it's been mentioned more than a few times, and why some people think the truck will "auto correct" for tire size changes.

 

[John Jensen]

You don't understand what is going on.
Carplay just means your car is connected to your truck and sharing data, you can open apps while Carplay is connected.

The problem is not the app, or kind of app you use. It's about how you are or are not connected to your truck.
2022 and above also use wireless Carplay also.

Carplay isn't an app, and if plugged in through USB with Carplay running, some apps, for some reason, will default to vehicle speed sensor. it's been mentioned more than a few times, and why some people think the truck will "auto correct" for tire size changes.

Okay

 

[theblet]

Long story short, if you’re gonna use your phone to compare mph against your truck, just don’t plug in the usb during the test. That’s your best bet.

 

[Rodger1966]

Update: 295/65-20 BFG KO2's ended up at 2700-MM as a circumference that is spot on.