MOJAVE; Turns out I do not need to adjust/recalibrate speedometer running 37s.

[TJDave]

My Rubicon. Stock 33's to 35's, speedo is off about 4 mph per my phone GPS, and the little speed info trailers put out by the local PD. I'm sure it is also effecting my Jeep's dash mpg readings, but everything else is livable until I go to 37's. Then, I will have a Tazer Mini.

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[jeepit]

just like Renegade said
having phone plugged into usb was causing it to be same
when unplugged damage is 5 miles give or take.
thank ya’all

 

[AzRob]

just like Renegade said
having phone plugged into usb was causing it to be same
when unplugged damage is 5 miles give or take.
thank ya’all

Im one of those people that is against leaving stuff in, and hooked up to the Jeep 24/7 so I decided to go with the JScan phone app, instead of the Tazer.

I bought the two parts needed on Amazon and the $19 app license... all in was about $90 and took about 10-15 minutes the first time. Dialed it in perfect and the speedometer is accurate all the way up to 90mph. When your done you take it out and it leaves no parts in the vehicle and no trace that you did anything.

Heres a link below that myself and many other have used to learn about it.... I was even posting on the last page with pictures and instructions this week. (The last page is a good place to check out first)

https://www.jeepgladiatorforum.com/forum/threads/please-teach-me-about-jscan.33495/

Hope this helps...Good Luck.

 

[ShadowsPapa]

My iPhone stays plugged into the USB and I use WAZE all the time with my business driving. I can say without a doubt that it does not go by the Jeep speedometer. The Jeep's speedo is calibrated to read a little slower than the GPS. It's about 1 mph difference at 60, and the difference increases with speed.

Differences are always in percentages so what you state makes perfect sense. That means that at 30 mph, the difference would be less than 1 mph and at 80 it would be more than 1 mph.

 

[Renegade]

just like Renegade said
having phone plugged into usb was causing it to be same
when unplugged damage is 5 miles give or take.
thank ya’all

 

[ShadowsPapa]

So why were those two the only ones to see the phone sync up with the Jeep? How would a phone app pull the info from the truck's system? Moreso - WHY would it?
What APP was it?
Mine sure never does such a thing. That means it would be reading from the CANBus instead of its own internal GPD/location services.

 

[Renegade]

So why were those two the only ones to see the phone sync up with the Jeep? How would a phone app pull the info from the truck's system? Moreso - WHY would it?
What APP was it?
Mine sure never does such a thing. That means it would be reading from the CANBus instead of its own internal GPD/location services.

I can’t answer why an app designer would write the program a certain way. All I know is that mine does it. Maybe it’s an iPhone thing?

 

[ShadowsPapa]

I can’t answer why an app designer would write the program a certain way. All I know is that mine does it. Maybe it’s an iPhone thing?

That may be it - who knows!
More interesting to me is that the app can even access that part of the JT - that's not just the radio it's talking to in order to get that info. It's not the GPS it's talking to. It's the JT's internal architecture it's talking to. That's the sort of information the OBDII port gives out to readers.
To think that someone can connect something USB and get info other than what the RADIO/NAV system has is interesting.

 

[Renegade]

That may be it - who knows!
More interesting to me is that the app can even access that part of the JT - that's not just the radio it's talking to in order to get that info. It's not the GPS it's talking to. It's the JT's internal architecture it's talking to. That's the sort of information the OBDII port gives out to readers.
To think that someone can connect something USB and get info other than what the RADIO/NAV system has is interesting.

Your infotainment system accesses and logs MUCH more than most people are aware of. There are companies who make systems to retrieve this data for use in legal issues.

 

[ShadowsPapa]

Your infotainment system accesses and logs MUCH more than most people are aware of. There are companies who make systems to retrieve this data for use in legal issues.

Yeah, such as accident investigations, etc. - who actually was speeding, who was stopped and so on.
I know a guy who's butt was saved by the retrieved info after he was sued and blamed for causing an accident. He was thankful they did collect that info.

 

[jbmdux]

Mojave running 37s with -12 offset wheel, no lift, full turns are perfectly clear.
also turns out I do not need to adjust/recalibrate speedometer jumping from 32s to 37s.
Comparison I made was with waze and other speedo apps before and after and it is still accurate without any adjustment.
Looking at 2" AEV spacer lift but it seems 1" all-around would be good enough for my level of off-roading if available.

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Test it on a known distance like a measured mile. There is no way your odometer is still correct and subsequently your speedo

 

[Renegade]

Test it on a known distance like a measured mile. There is no way your odometer is still correct and subsequently your speedo

Yeah, he already figured out the issue.

 

[Mcguyvr]

Also recently did a few recals. After dealer flashed with superchip to accommodate my Nitto Ridge Grappler 37s....everyone else on the road was flying past me with cruise set at 52 in a 45(ish) daily drive.

GPS check confirmed that it was off nearly 6-7mph. When I measured tire height, the 37s are actually 36-35.5” in real life on-the-truck (only ~600mi on them).

After dialing it in by .25” at a time and testing against speed control, GPS, and local roadside speed trailer, I can say I’m happily within .25mph for most of the driving mph range.

Uncorrected, The error will, over time Rack up the false miles and inaccurate economy readings.

Don’t just accept dialing your tires in by what they are labeled.

As for the USB making your iPhone read the truck? Yeah...I’m gonna call fake news! But I will try it out tonight. There’s black box units the police / insurance nabs for their needs. I’ll regret posting this I’m sure with further backlash from any of you IT ‘experts’ out there but I’m highly suspect my Regular ole iPhone can tap into or read the truck info from a USB charge port.

 

[Renegade]

Also recently did a few recals. After dealer flashed with superchip to accommodate my Nitto Ridge Grappler 37s....everyone else on the road was flying past me with cruise set at 52 in a 45(ish) daily drive.

GPS check confirmed that it was off nearly 6-7mph. When I measured tire height, the 37s are actually 36-35.5” in real life on-the-truck (only ~600mi on them).

After dialing it in by .25” at a time and testing against speed control, GPS, and local roadside speed trailer, I can say I’m happily within .25mph for most of the driving mph range.

Uncorrected, The error will, over time Rack up the false miles and inaccurate economy readings.

Don’t just accept dialing your tires in by what they are labeled.

As for the USB making your iPhone read the truck? Yeah...I’m gonna call fake news! But I will try it out tonight. There’s black box units the police / insurance nabs for their needs. I’ll regret posting this I’m sure with further backlash from any of you IT ‘experts’ out there but I’m highly suspect my Regular ole iPhone can tap into or read the truck info from a USB charge port.

Why is it that people who haven’t done something seem to think they know more than people who have? Are you using the exact same app? If not, your test is shit.
Edit: Actually it’s not fake news, it OLD news. Here:
https://www.jlwranglerforums.com/forum/threads/self-correcting-speedometer.12753/

 

[DreamedofaJeepSomeday]

. . . I’m highly suspect my Regular ole iPhone can tap into or read the truck info from a USB charge port.

Well, that's the thing. There are USB charge ports but there is also the USB media port. That surely can do a lot more than charging.

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