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

ShadowsPapa

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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/
VERY interesting on the iPhone app synching to the Jeep's speedo reading. I guess I could see that as it's assuming your Jeep speedometer is accurate and it's getting a direct speed reading instead of relying on GPS which can LAG a bit - you can speed up and it may take a second for GPS to relfect your new speed. I've seen that several times.

Let me toss this at you (I'm convinced that at least the APPLE phones do that (my android, naw, not with the apps I use anyway. Proof is those who unplug their phone and see them disagree after that. )
- question -
Why is it that the analog speedometer on the right side of the cluster always reads HIGHER than the digital readout on the center if I choose to view that?
I don't normally display the speed on the center part, it's redundent IMO - I have that analog speedometer on the right, why do I need it in print in the middle?
But when I first got the truck, and even now if I flip through the displays and have both up at the same ti
The digital may say RIGHT ON 55 while the analog gauge shows 57.
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#HuckleberryJeep

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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.

View attachment 111973

View attachment 111981
Good-lookin' JT man. Try running the Waze app while it's not plugged in. You'll see a difference then. I had the same result when I first upgraded tires too.
 

betsy

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JL /JT are very forgiving, unlike JKS , but you still need to calibrate , it will affect shift points, try the old fashioned way, use the mile markers on the interstate and your trip meter, it will be pretty close !
 

Mcguyvr

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Renegade

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Jaysus Zac. I told ya i'd try it out. Some of us don't have all day to post 2500 times trolling forums and work for a living. WTH chill.
Yep, that’s me, I’m a troll who doesn’t work for a living. The problem is that you crapped on valid information with absolutely no experience on this subject. I treat this forum as an encyclopedia (for the millennials, those were a series of reference books people used to buy before the internet existed) for Jeepers, and wouldn’t post something like that unless I had knowledge of it. Welcome to the forum by the way...
 
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RubiCrusHehr

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Was your phone plugged into the usb on the dash when taking your measurements? If so, it will read the Jeep’s speedometer rather than actual gps speed.
Exactly, I experienced it since the last 5 or so years starting with 2 last JK's
 

ShadowsPapa

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After being told directly more than once, even reading other threads "Jeep speedometers are always off anyway" or "they always read this way" or whatever, I decided to run a test. I needed to make a trip into town for some supplies for restoration projects, so fired up my phone and my Garmin GPS.
To ensure no interaction (the Garmin is dumb in that way anyway, it can't interact and when plugged into USB, it drops to charging mode and shuts off) I didn't plug any device into anything at all. I made sure batteries were charged in everything.
Phone laying in the cup holder area, not plugged in, GPS suctioned to the windshield so I could watch it and the cluster at the same time.
I drove around a while and turned my cluster display to show the big digital speedometer and trip counter A.
I watched the GPS, phone and JT speedometer and was amazed - they synced up near perfectly. When I put on cruise (I chose easy round numbers) they stayed in lockstep. When the speedometer dropped 1, so did the others. If it gained 1 mph, so did the others.
I got to O'Reilly's, did my shopping, wrote down what was on the trip counter for miles (262)and took the long way home to ensure I wasn't comparing odometers over just a mile or 10.
When I got back, I took photos of the GPS (used my phone so no, don't have that pic - forgot to take a screenshot first) and of the JT's cluster.

Note that I started at 262 miles on Trip A
Note the miles now at Trip A and on the GPS -

262 + 13.5 = 275.5 , correct?
And the GPS says 13.5, right?
Perfect match over 13 miles. And the speedometer SPEED reading in mph also matched.
No possibility that older Garmin could sync with that new JT - no way in heck. I even have bluetooth turned off on the Garmin.
There was no cable in my phone, and bluetooth wasn't connected on it, either.

So - you guys may have JTs that have inaccurate speedometers and odometers, but not me.
Please stop saying they are all off or wrong.
To be lined up to the very tenth of a mile after 13 miles of driving is pretty good. I guess if I get a ticket, it's my own fault, can't blame the stupid speedometer!


Jeep Gladiator MOJAVE; Turns out I do not need to adjust/recalibrate speedometer running 37s. 20201027_112712_HDR


Jeep Gladiator MOJAVE; Turns out I do not need to adjust/recalibrate speedometer running 37s. 20201027_112659
 
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jeepit

jeepit

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Thanks AzRob
Went ahead and got the tire size updated.
per discount tire website, actual tire diameter 36.77"
my measurement, mounted diameter 35.75" @ 37psi cold tire pressure
JScan value of 35.75" or 36" @ 37psi gave me similar reading around ~ +/- 1 mile
I think there maybe GPS lag in cloudy days but after sec or two of steady speed it matches to phone speedometer apps.
so went with value 36", it may even out in summer and when tire pressure goes up when driving bit longer.

Overall pretty straight forward 5 mins job, pita is to disconnect and reconnect those wires.

3-things
1. OBD JScan app subscription.
2. FCA 12+8 Universal Adapter Cable Adapter
https://www.amazon.com/gp/product/B082PTBZ6K/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1
3. OBD2 Bluetooth Code Reader
https://www.amazon.com/gp/product/B06XGB4873/ref=ppx_yo_dt_b_asin_title_o00_s00?ie=UTF8&psc=1

Helpful youtube video



my Mojave still handles comparable to stock, not a dog yet with those big tires.:jk:
 
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ShadowsPapa

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There's often some lag, on mine it's typically about half a second but it's the same up or down, so it evens out to spot-on in the end. If you set cruise on a level road these trucks will stay pretty set on speed - that's how I checked mine and it stayed exactly at 50 for several seconds, so did phone and GPS. And - the mileage on the odo matched, confirming accuracy (as close as is possible on mechanical things)
 

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You guys and your gadgets !
 

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ShadowsPapa

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You guys and your gadgets !
You haven't seen gadgets yet.......... I have a pH meter than sends the readings to my phone and records in a log. I use that for my plating processes.
For a while I used a bluetooth bridge - cell phone calls would end up on phones in the house, and if you made a call on a house phone, it went out over our cell phones. Double ring for my cell phone, single ring for my wife's cell phone, so we knew which phone was being called. We decided we didn't really need it any more so pulled it and removed all of the phones in the house on the wire.
I have a DVR on my network that has 4 tuners, and will play recorded shows on any TV in the house - or in my shop, or on my tablets or phone. I can record 4 shows at once, or record one and play different shows on 3 different TVs or other devices.
I can export them to a big network drive I have. I made some recordings and exported them to my tablet for viewing on my flight to Korea a couple of years ago.
My hearing aids link to my phone directly. Don't even need the bluetooth in the truck (it doesn't work for texts anyway so why bother - I get a text from my wife and the truck doesn't alert me. It's never worked correctly) My phone can be upstairs and I can be down - and answer my phone with the push of a button.
 

Mcguyvr

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Shadow pops - thanks for the work you did in testing all that. I ended up doing much of the same with 3 devices, plugged in and not plugged in after Ren's shaming (despite my foreshadowed comments in OP).

I used Google Maps, Apple Maps, and 2 different speedo Apps, CARPLAY and NOT CARPLAY. None changed plugged in or not. I have not tried WAYZ or know what APPS others may be experiencing with the DRO jumping to live truck speed vs GPS - but mine performed as your tests and as expected off GPS only (and got tires dialed in to match). Thanks for your posts and dedication to this forum BTW.
 

betsy

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What about shift points?
 

ShadowsPapa

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Shadow pops - thanks for the work you did in testing all that. I ended up doing much of the same with 3 devices, plugged in and not plugged in after Ren's shaming (despite my foreshadowed comments in OP).

I used Google Maps, Apple Maps, and 2 different speedo Apps, CARPLAY and NOT CARPLAY. None changed plugged in or not. I have not tried WAYZ or know what APPS others may be experiencing with the DRO jumping to live truck speed vs GPS - but mine performed as your tests and as expected off GPS only (and got tires dialed in to match). Thanks for your posts and dedication to this forum BTW.
There are many days I suspect that's why I even exist.
But you may not like my findings on the Mopar trailer brake controller LOL
Been a LONG day. 2:15 - time for lunch.
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