Am I overthinking this?

Shoebox303

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Hey guys - I just put 37” tires on my JLU and also bought a Tazer to recalibrate the speedometer. The 37” procomps actually measure 36” with the weight of the Jeep on them. I’m assuming the diameter is more than 36” WITHOUT the weight of the vehicle. The Tazer can get VERY specific with tire diameter calibration.

So here’s my question. Should I:
  1. calibrate the speedometer to the tire diameter *with* the vehicle load
  2. calibrate the speedometer *without* the vehicle load, or
  3. just go have a beer and watch a baseball game and quit overthinking this.
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Xcoaste

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I would use what the sidewall of the tire indicates
 

Spank

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Hey guys - I just put 37” tires on my JLU and also bought a Tazer to recalibrate the speedometer. The 37” procomps actually measure 36” with the weight of the Jeep on them. I’m assuming the diameter is more than 36” WITHOUT the weight of the vehicle. The Tazer can get VERY specific with tire diameter calibration.

So here’s my question. Should I:
  1. calibrate the speedometer to the tire diameter *with* the vehicle load
  2. calibrate the speedometer *without* the vehicle load, or
  3. just go have a beer and watch a baseball game and quit overthinking this.
#1 and #3, but not in any specific order.

No GPS speedometer or doppler sign is perfect, but entering a value that is larger than the actual, physical tire size just to get it to match readings eventually adds up on your odometer because you're adding mileage that doesn't exist.

I don't know what size Jeep calibrates non-BFG tires, but they don't set it to the rated size on the Rubicon. The 33" KO2s, for example, typically measure 31.5" on load and they set it to this value.
 

WilhelmSR

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hold up.... You can work on your Jeep without having a beer?

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WranglerMan

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This is what I did when I ran a Tazer, I set the size with the Tazer program to the closest size of the tire and then rebooted and took it for a drive and then used the Speedbox app to check my speed and then went back in and made additional adjustments, it only took a few tries to get it within a mile of being correct
 

0II392II0

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I'll be getting one in the near future and would like to hear what you end up setting it on.
 

1idrod

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I've measured from the center of hub to the ground and multiplied by 2 and it puts me pretty damn close.
 

Rogueman_1

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I use my OBD JScan app on my phone to do all sorts of stuff including recalibrate the tire size when I went to 37's. 37's generally measure out to 36 on the rig so that's what I re-calibrated it to. Seems spot on.
 

Yogi

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Does that Tazer actually ask for the tire size, or does it ask for the revolutions per mile?
i.e. the 35" KO2 runs at 602 revolutions per mile as published by the manufacturer.
 

1idrod

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Does that Tazer actually ask for the tire size, or does it ask for the revolutions per mile?
i.e. the 35" KO2 runs at 602 revolutions per mile as published by the manufacturer.
Tire size
 
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