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Speedometer issue?

Ktm150xcwtpi

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Will someone explain how I put 34” tires on my 22 ram and now my speedo reads Higher/faster than the Waze app on my touch screen, and another gps speedo on my phone? I’m going farther with the bigger tires, so logic says my speedo should read slow. That’s how it’s always been in my experience. Dash reads 80 mph while Waze says 76. How is my speedometer fast???? Pic for attention
 

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Idahoktm

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Will someone explain how I put 34” tires on my 22 ram and now my speedo reads Higher/faster than the Waze app on my touch screen, and another gps speedo on my phone? I’m going farther with the bigger tires, so logic says my speedo should read slow. That’s how it’s always been in my experience. Dash reads 80 mph while Waze says 76. How is my speedometer fast???? Pic for attention

Next time you go out, use the GPS app on your phone but turn off the Bluetooth and don't plug your phone into a data port. If your phone is connected to UConnect, it won't read accurately.
 

Ktm150xcwtpi

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Next time you go out, use the GPS app on your phone but turn off the Bluetooth and don't plug your phone into a data port. If your phone is connected to UConnect, it won't read accurately.
Thanks fellow Ktm fan! I’ll give that a go. (Pic of my babies)
 

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Darksteel165

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I just realized my speedo is off toay. Going 71mph but truck says 69mph.

I changed my speedo to the correct tire size in Alfaodb (it was set for wheels that come on a 4500 so set it to the wheels\tires that came on my truck from the factory as it had an exact match but no dice)

If I can live with it, it's technically better as I drive more miles then get recorded LOL.

80-76 is a pretty big difference though.

You know maybe I will keep my spedo fine, maybe use it to get out of a speeding ticket by having an shop confirm my speedometer was incorrect.
 

HSKR R/T

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I just realized my speedo is off toay. Going 71mph but truck says 69mph.

I changed my speedo to the correct tire size in Alfaodb (it was set for wheels that come on a 4500 so set it to the wheels\tires that came on my truck from the factory as it had an exact match but no dice)

If I can live with it, it's technically better as I drive more miles then get recorded LOL.

80-76 is a pretty big difference though.

You know maybe I will keep my spedo fine, maybe use it to get out of a speeding ticket by having an shop confirm my speedometer was incorrect.
That won't be a valid excuse, especially since you know it's off. My tire size according to alfaObd didn't match my actual tire from factory either, but speedometer was correct. Wasn't a need to change it until I changed tire size. And even then, when I selected the actual tire size I installed, the speedo was about 5 mph off. I kept changing size ubtil I found one that worked. When I went from the 275/65/20 to the 35x12.50/20's, I used my TazerDT. Was much easier, I selected the different diameter until I got to one that worked. But it's all through steering wheel controls.
 
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Ktm150xcwtpi

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Still reading slower on my touch screen Waze app. I’ll get my wife to ride with me on the interstate with cruise at 80 and see what’s what.
 

Darksteel165

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That won't be a valid excuse, especially since you know it's off. My tire size according to alfaObd didn't match my actual tire from factory either, but speedometer was correct. Wasn't a need to change it until I changed tire size. And even then, when I selected the actual tire size I installed, the speedo was about 5 mph off. I kept changing size ubtil I found one that worked. When I went from the 275/65/20 to the 35x12.50/20's, I used my TazerDT. Was much easier, I selected the different diameter until I got to one that worked. But it's all through steering wheel controls.
I am using OEM wheels and tires, Alfaodb matches the exact brand and size of the tires. I think it's odd Ram has that setting there, but they know it's incorrect which is why it got set to some random wheel form the factory that can't even come on a 1500, 2500, or even 3500. I'm also ASSUMING it was correct BEFORE I changed it, but I never bothered to check.

At least in my state if I can prove my speedometer is wrong by a mechanic (doesn't need to be dealership) it generally voids a speeding ticket.
The court would have 0 reason to assume I knew it was off.
Obviously if it's only 3 MPH off and i'm going 40 over the limit it isn't going to matter.

If I wasn't on these forums I don't think I would ever care to check even if I changed tires\wheels for the better or worse.
 

Idahoktm

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Still reading slower on my touch screen Waze app. I’ll get my wife to ride with me on the interstate with cruise at 80 and see what’s what.

It's not going to read the correct speed until your speedometer has been recalibrated. I know that doesn't explain the GPS app reading slower than your speedometer. The only way to know your true speed is to use an independent GPS.
 
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VectorZ

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You may be interested to know the actual federal law in this matter.

49 CFR § 393.82 - Speedometer.​

§ 393.82 Speedometer.
Each bus, truck, and truck-tractor must be equipped with a speedometer indicating vehicle speed in miles per hour and/or kilometers per hour. The speedometer must be accurate to within plus or minus 8 km/hr (5 mph) at a speed of 80 km/hr (50 mph).
[70 FR 48054, Aug. 15, 2005]
 

HSKR R/T

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You may be interested to know the actual federal law in this matter.

49 CFR § 393.82 - Speedometer.​

§ 393.82 Speedometer.
Each bus, truck, and truck-tractor must be equipped with a speedometer indicating vehicle speed in miles per hour and/or kilometers per hour. The speedometer must be accurate to within plus or minus 8 km/hr (5 mph) at a speed of 80 km/hr (50 mph).
[70 FR 48054, Aug. 15, 2005]
This is why most people will do 5mph over posted speed and not worry about it, because the speedometer is not required to be that accurate
 

Darksteel165

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You may be interested to know the actual federal law in this matter.

49 CFR § 393.82 - Speedometer.​

§ 393.82 Speedometer.
Each bus, truck, and truck-tractor must be equipped with a speedometer indicating vehicle speed in miles per hour and/or kilometers per hour. The speedometer must be accurate to within plus or minus 8 km/hr (5 mph) at a speed of 80 km/hr (50 mph).
[70 FR 48054, Aug. 15, 2005]
You may be interested to know that that federal law does not apply to cars\passenger trucks (pickups) so that has nothing to do with our Rams. You even posted it right in your quote "Each bus, truck, and truck-tractor"

This is why most people will do 5mph over posted speed and not worry about it, because the speedometer is not required to be that accurate
Not really. Most cops don't pull over unless you are going 11 over the limit, at least state cops because it isn't worth the hassle, or so several cops I have met over the years have told me.
They can pull you over for 1 mph over the limit and ticket you if they wanted, you would fight and win though.
 

HSKR R/T

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You may be interested to know that that federal law does not apply to cars\passenger trucks (pickups) so that has nothing to do with our Rams. You even posted it right in your quote "Each bus, truck, and truck-tractor"


Not really. Most cops don't pull over unless you are going 11 over the limit, at least state cops because it isn't worth the hassle, or so several cops I have met over the years have told me.
They can pull you over for 1 mph over the limit and ticket you if they wanted, you would fight and win though.
I've been pulled over for less than 10mph over limit. A lot depends on what the actual posted speed is. Doing 10 over in a 35mph zone will get you a ticket faster than 10 over in 70mph zone. Or if the officer is just looking for a reason to pull you over.
 

Darksteel165

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I've been pulled over for less than 10mph over limit. A lot depends on what the actual posted speed is. Doing 10 over in a 35mph zone will get you a ticket faster than 10 over in 70mph zone. Or if the officer is just looking for a reason to pull you over.
"state cops". I don't know any state roads that are 35 mph at least in my part of the country.
A cop can pull you over for whatever they want. They could claim you were going 140 in a 20 if they wanted, the ticket would just get thrown out.
 

Ktm150xcwtpi

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My wife’s speedo app showed 75mph while my dash speedometers were both 5 mph slower. So until I get it calibrated, I’ll just go no more than 5 over.
 

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