Tire size change - can’t get at programming cables.

[Zachanadandy]

Tire crown or not a direct straight across measurement. I was specifying the best way, Not necessarily the simplest way. Slight angle over 35in could change your measurement 1/4in to 3/4in.

Depending on the weather, I'll just guess and verify with GPS. Adjust from there. Are you measuring circumference with weight on the tire? If not I'd argue diameter would be more accurate to actual rolling diameter anyway.

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[Mojave2021]

I had the same problem. That support bar and my bad shoulder, torn rotator cuff... made it really hard so I asked my son to reach up there and damn he did it with ease!

Maybe just ask someone for help and let them know what to do.

Best of luck!

Good idea - will see if my 16 year old can get in there?

 

[Dickster]

Depending on the weather, I'll just guess and verify with GPS. Adjust from there. Are you measuring circumference with weight on the tire? If not I'd argue diameter would be more accurate to actual rolling diameter anyway.

Good thing about measuring the circumstance vs diameter is the Tire will inlongate making a bigger contract patch under load. which will shorten your diameter, but the Tire will still have the same distance around.

 

[Zachanadandy]

Good thing about measuring the circumstance vs diameter is the Tire will inlongate making a bigger contract patch under load. which will shorten your diameter, but the Tire will still have the same distance around.

Not sure I agree, as the vehicle travels on the elongated portion. If you measured actual distance traveled per rotation I'd bet it is not the same as the unloaded circumference. Maybe if I'm really bored one day I'll mark the tire where is touching the ground and roll the vehicle forward exactly one rotation and take a measurement but in my mind that would be the most accurate in the real world.

 

[Mojave2021]

Ok I managed to get it off and reprogrammed it. The JScan app says to open and close the door, then close it again and leave it be for 5 minutes. I thought I was supposed to click the restart all ECUs button from the videos. Assuming the door maneuver must do the same thing?

 

[Dickster]

Not sure I agree, as the vehicle travels on the elongated portion. If you measured actual distance traveled per rotation I'd bet it is not the same as the unloaded circumference. Maybe if I'm really bored one day I'll mark the tire where is touching the ground and roll the vehicle forward exactly one rotation and take a measurement but in my mind that would be the most accurate in the real world.

Put load on the Tire and measure height. Then measure width and I bet the measurements are way different. Tire is only elongated on the contact patch and that will be it. Once off it will form back to original diameter. This has been a topic for awhile back when Alphaobd was one of the first tool out. To change Tire is was in circumstance in millimeters.

 

[Dickster]

Ok I managed to get it off and reprogrammed it. The JScan app says to open and close the door, then close it again and leave it be for 5 minutes. I thought I was supposed to click the restart all ECUs button from the videos. Assuming the door maneuver must do the same thing?

It took tazer 3 times for mine to take.

 

[Zachanadandy]

Put load on the Tire and measure height. Then measure width and I bet the measurements are way different. Tire is only elongated on the contact patch and that will be it. Once off it will form back to original diameter. This has been a topic for awhile back when Alphaobd was one of the first tool out. To change Tire is was in circumstance in millimeters.

But like I said, you only drive on the loaded portion so I'd argue that is the rolling circumference relevant to actual distance traveled. The Jeep is only counting rotations via the tone rings, the rest is math based of distance traveled per rotation. The traveling part is 100% on the loaded portion of the tire.

 

[fourfa]

Not much to add here, it’s hard and it sucks. I would also advise anyone that has to do it once, get the extension cables so you never have to do it twice.

One interesting thing: if you plan to have your front left speaker pod out (the 4” midbass in the knee panel), the security module you’re trying to unplug is screwed into the back of it. While you’re in there, don’t screw it back in where it’s impossible to get to, ziptie it over to the left where you can reach it better.

If you think the SGW access is bad wait until you get that left speaker pod out…

 

[Sw00per]

Good idea - will see if my 16 year old can get in there?

Best of luck! BTW

Ok I managed to get it off and reprogrammed it. The JScan app says to open and close the door, then close it again and leave it be for 5 minutes. I thought I was supposed to click the restart all ECUs button from the videos. Assuming the door maneuver must do the same thing?

I am interested to see what you need to change from and what you change to. After doing my measurement then using GPS it came to 33.40 up from 31.0 which is going form the stock Falkens to the BFG K02's.

 

[Mojave2021]

Success! It took the change the first time and 33.75” looks to be spot on as my gps app and Speedo match now.

To get the cables out I used my finger to pinch the connector loose and used a pair of pliers to pull down the cable at the same time. In addition to removing the under steering panel. Not rocket science.

Just a couple of cuts on my fingers. Managed to get them back in (easier for me than pulling them out) but agree that I need to get some extension cables if I plan to do any future adjustments. I don’t have any plans for now though.

The JScan app works great. Costs $20 for my vin.

FYI my tires are 315/70/17 Ridge Grapplers on 17x9.5 wheels. So they’re stretched out a bit and I do have a Rock Hard steel rear bumper and an RH 4x4 aluminum front bumper. Those are my only weight related mods.

 

[ShadowsPapa]

Well seeing how your speedo works on circumstances not diameter why not? Jscan and tazer already have it calculated out for you to make it easy but if you enter the wrong info it will be wrong. Alfaobd will run off millimeters of the circumstance.

Circumstance?

Circumference.....

VehConfig 4:
___________________
Transfer Case High Ratio (0-16.382): 1.000
Axle Ratio (0-65.534): 3.730
Transfer Case Low Range Reduction Ratio (0-65.534): 2.720
Dynamic Tire Circumference (All or Rear) (0-65534 mm): 2508.000 mm

 

[ShadowsPapa]

But like I said, you only drive on the loaded portion so I'd argue that is the rolling circumference relevant to actual distance traveled. The Jeep is only counting rotations via the tone rings, the rest is math based of distance traveled per rotation. The traveling part is 100% on the loaded portion of the tire.

Yes, rolling or dynamic circumference. But the software has you enter diameter (usually closest number will be with tire loaded on the ground, ground to top) and the software converts for you.
Sometimes it takes a try or two.
I changed mine 2 times after the initial number - but I went by miles/distance traveled for a perfect match. Odometer/trip meter reset, and used a GPS app to measure distance traveled until I got to a perfect match between the two.
17.2 miles on the trip odo and 17.2 miles on the phone app. Close enough.

Note my post about how it shows up in the actual programming -

(this was taken from a Jeep a long while back, can't recall which one)
VehConfig 4:
___________________
Transfer Case High Ratio (0-16.382): 1.000
Axle Ratio (0-65.534): 3.730
Transfer Case Low Range Reduction Ratio (0-65.534): 2.720
Dynamic Tire Circumference (All or Rear) (0-65534 mm): 2508.000 mm

 

[Camaroboi13]

I was waiting for someone to correct the four circumstances ?

 

[Dickster]

I was waiting for someone to correct the four circumstances ?

Cellphone auto correct what can say ?‍

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