X

[azmojave]

X

Sponsored

 

[JT1]

So I upsized from 33 to 35 tires and I figured my Speedo would be off until I get an adjuster. On my way home, cruise was at 65 and waze said 69. The next day I took a little road trip and noticed something strange. Here’s two quick snapshots I took (wife’s phone, eyes on the road lol) and you can see my cruise setting, my analog speedo and waze all at the same time. Thoughts?
View attachment 305637 View attachment 305638

Unplug your phone. Turn off the blue tooth and run Waze. It will tell you your speed via GPS. Then compare to what the jeep says. It will be different.

When your phone is connected like that, the jeep changes to match.

 

[ATL_Rubi]

Mine is calibrated, but every so often, Waze/My Radar Detector will show 2-3 faster.

 

[Lunentucker]

I had to change mine using ECRI. It never matched until I did.
I'm pretty sure WAZE doesn't talk to U-Connect outside of it's being allowed to use the display screen. That would be a security disaster.

 

[Lunentucker]

Your analog gauge is actually displaying about +2 in both pics. Switch your center digital to display MPH for pinpoint accuracy.

 

[Lunentucker]

There's also an inherent delay in Waze displaying what the truck is doing. About a second on mine. So when it's properly calibrated you'll see the Jeep hits 70 about a second before Waze displays 70.

 

[yoda13]

My speedometer is still off after going to the 35s. I have a Tazer, but I only tried to install it once and all I did was cut myself up. Now that I have the proper long slim nosed pliers, I am going to install it soon.

 

[Trollboogie]

I used an ECRI. Uses GPS to calibrate speed. Mine now perfectly matches my Waze.

 

[Mr._Bill]

My speedometer is still off after going to the 35s. I have a Tazer, but I only tried to install it once and all I did was cut myself up. Now that I have the proper long slim nosed pliers, I am going to install it soon.

Get the ZAutomotive extension cable set so that you only have to do it one time.

 

[yoda13]

Get the ZAutomotive extension cable set so that you only have to do it one time.

Didn’t even know such a thing existed. I will grab me one. Thank you!

 

[Darkamek]

If your town has a radar detector mounted to display if your speeding on a road. You could drive past that and compare it to your dash. I did this after I measured my tire size and adjusted it with the Tazer. It worked out pretty well, within 1 mph.

 

[briscoelab]

Unplug your phone. Turn off the blue tooth and run Waze. It will tell you your speed via GPS. Then compare to what the jeep says. It will be different.

When your phone is connected like that, the jeep changes to match.

It's actually the other way around. When connect to CarPlay, Waze or GoogleMaps will display the speed the Jeep thinks it's going. It's a weird quirk for sure.

It almost cost me a ticket last year, after the dealer flashed my computer and I didn't realize it. Running 80mph indicated on a road trip, flying past cars like crazy... wondering why everyone was going so slow. Unplugged the USB and Waze immediately went to 89mph. Oops.

Lots of people have posted similar stories to the OP. "oh my speedo wasn't off at an all when I switched to 35s." Be careful out there! haha

You can verify this for yourself if you have a tazer, pro cal, etc. Just set your tire size wrong and plug in your phone. The CarPlay nav apps will give the speed from the Jeep.

Also, an easy way to dial in your calibration... without having to measure anything:

1. Go out on a straight road and set cruise at a given speed (ie indicated on jeep 60mph).

2. Use a GPS speed program (Waze will work) with phone not connected to vehicle to get true speed.

3. Use the two speeds to calculate your % offset.

4. Increase your tire size setting by that %. Done!

This is useful since there is a lot of variation in actual tire sizes and it's not really that easy to measure a true tire size.

Take home message, set the tire size properly. It gets the speedo and shift points back in check.

 

[jeepit]

Unplug your phone. Turn off the blue tooth and run Waze. It will tell you your speed via GPS. Then compare to what the jeep says. It will be different.

When your phone is connected like that, the jeep changes to match.

This is 100% true, i had the same

 

[sharpsicle]

Unplug your phone. Turn off the blue tooth and run Waze. It will tell you your speed via GPS. Then compare to what the jeep says. It will be different.

When your phone is connected like that, the jeep changes to match.

This is 100% true, i had the same

Either of you have a source for this assertion? From what I see, the idea's been floated many times but it's never actually shown to be true in any objective way. Just situational anecdotes and "I think..."

It's a bold statement to say that an unregulated 3rd party device will override a part of the vehicle's safety system like a speedometer. If that's the case, that's a huge vulnerability. If Jeep actually did this, it's pretty negligent of them. In the past they haven't even allowed their own GPS systems to override the speedometer, so I find it hard to believe they'd let a random piece of attached equipment do it instead.

It's much more likely that the phone is reading the Jeep's speed as there's significantly less liability in allowing information to flow out rather than in.

But again, a source would be great for either assertion.

 

[briscoelab]

The phone gets the speed reading from the Jeep. The others are misinterpreting the observation of how car play works with regards to the displayed speed in nav apps.

This has been the case in all 3 of our Jeep’s with the 8.4 nav. 2020 JT, 2021 JL, 2023 JT.

You can verify this behavior very easily if you have a programmer to change tire size and an iPhone…. Or if you haven’t recalibrated your Speedo at all.

I can’t comment on how it works with android auto.

Sponsored