Is there a way to reset computer to relearn shift points?

What effect does the top half of the tire have on anything?


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When you are trying to get an exact measurement of your tire why would you only measure the lower half that also carries the weight of the vehicle and bulges out. That will definitely affect the total height if only measuring that side and then multiplying by 2. From the center of the the hub to the top of the tire is a larger measurement It is 2 different measurements




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The asshole who screwed everyone over by typing those instructions said so okay? lol

Eddie did a write up on how to accurately measure tires. Id start there

And Eddie recommends measuring to the top shoulder. Not to the center of the hub and multiplying by 2
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And Eddie recommends measuring to the top shoulder. Not to the center of the hub and multiplying by 2
View attachment 336088


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I wasn't specifically saying Eddie recommended this way, but if that's what you're looking for...

https://wayalife.com/showthread.php/22453-Strange-transmission-shift?p=413252&viewfull=1#post413252

I'm not gonna argue with you. I've done it every which way and the x2 method is dead-nuts accurate every time. Do you, though... I'll be over here happily enjoying an accurate speedometer and shift points. [emoji482]



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I’d think measuring the circumference using a roll out method would be more accurate than measuring diameters or radii. The circumference method would account for tire pressure and sag, among other things.


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..I've done it every which way and the x2 method is dead-nuts accurate every time. Do you, though... I'll be over here happily enjoying an accurate speedometer and shift points. [emoji482]



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Build Thread - Adventures of Fiona - https://wayalife.com/showthread.php?t=47407

I’d think measuring the circumference using a roll out method would be more accurate than measuring diameters or radii. The circumference method would account for tire pressure and sag, among other things.


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I still like my method the best... just involves a little more trigonometry.

IMG_1718.JPG
 
When you are trying to get an exact measurement of your tire why would you only measure the lower half that also carries the weight of the vehicle and bulges out. That will definitely affect the total height if only measuring that side and then multiplying by 2. From the center of the the hub to the top of the tire is a larger measurement It is 2 different measurements




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The point is rolling diameter is determined by the bottom half. The top half measurement has no effect so why include it


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I wasn't specifically saying Eddie recommended this way, but if that's what you're looking for...

https://wayalife.com/showthread.php/22453-Strange-transmission-shift?p=413252&viewfull=1#post413252

I'm not gonna argue with you. I've done it every which way and the x2 method is dead-nuts accurate every time. Do you, though... I'll be over here happily enjoying an accurate speedometer and shift points. [emoji482]



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Build Thread - Adventures of Fiona - https://wayalife.com/showthread.php?t=47407

I’ll say it, I need to remeasure with the X2 method. My tire height is set at the total height/flat edge method currently. I have a fairly steep grade near my house. Going downhill it’s fine. Uphill, won’t shift to 4th on its own at 70 MPH and 5000ish RPM. Doing this in the morning and I’ll report back!
 
The X2 method is definitely NOT the best way to measure tire size. The total tire height method using a bubble level mentioned by Turbo21 is better, and the roll out method suggested by Fiend is the most accurate. If you don't believe me, keep reading. BTW, Eddie's method referenced earlier is not intended for use in a programmer tool, but rather to establish a database of tire sizes that can be compared against each other.

The vehicle uses tire diameter to calculate circumference, and then revolutions per mile. Tires are not round, because they squat under load, so a NOMINAL diameter is required. The X2 and bubble level methods are only approximations for this nominal diameter. Even when squatting, however, the tire circumference does not change, so the most accurate method to obtain the nominal tire diameter is by directly measuring the circumference under load and calculating the nominal diameter. (This is a bit like approximating the circumference of the tracks on a battle tank using a circle with nominal diameter.) I tried this on my rig using painters tape and a tape measure and compared to the other methods on the same tires to show the differences. The table below summarizes the results. Notice that the bubble level method gives half the error as the X2 method, and the nominal tire diameters for the X2 method are underestimated by as much as 1.70 - 1.90".

Tire Measurments.jpg

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IMG_4871.JPG

IMG_4876.JPG

IMG_4877.JPG

The jeep weighs 5500 lbs at the time of measurement, and is running stock BFG Mud Terrain T/A P255/75/R17 tires with 60,000 miles on them. Measurements were done at an elevation of 100 feet at 90F.
 
The X2 method is definitely NOT the best way to measure tire size. The total tire height method using a bubble level mentioned by Turbo21 is better, and the roll out method suggested by Fiend is the most accurate. If you don't believe me, keep reading. BTW, Eddie's method referenced earlier is not intended for use in a programmer tool, but rather to establish a database of tire sizes that can be compared against each other.

The vehicle uses tire diameter to calculate circumference, and then revolutions per mile. Tires are not round, because they squat under load, so a NOMINAL diameter is required. The X2 and bubble level methods are only approximations for this nominal diameter. Even when squatting, however, the tire circumference does not change, so the most accurate method to obtain the nominal tire diameter is by directly measuring the circumference under load and calculating the nominal diameter. (This is a bit like approximating the circumference of the tracks on a battle tank using a circle with nominal diameter.) I tried this on my rig using painters tape and a tape measure and compared to the other methods on the same tires to show the differences. The table below summarizes the results. Notice that the bubble level method gives half the error as the X2 method, and the nominal tire diameters for the X2 method are underestimated by as much as 1.70 - 1.90".

View attachment 336191

View attachment 336192

View attachment 336193

View attachment 336194

View attachment 336195

The jeep weighs 5500 lbs at the time of measurement, and is running stock BFG Mud Terrain T/A P255/75/R17 tires with 60,000 miles on them. Measurements were done at an elevation of 100 feet at 90F.

I love having a real engineer around.

I just get to fake being one from time to time.


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Which ever method you use it's best to double check the accuracy with a GPS. The speedo and GPS should match. I had to make a couple adjustments to get it correct. I used the level method. I believe I had to increase the size a bit. It's been too long since I sold it do I do not rememeber.

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Which ever method you use it's best to double check the accuracy with a GPS. The speedo and GPS should match. I had to make a couple adjustments to get it correct. I used the level method. I believe I had to increase the size a bit. It's been too long since I sold it do I do not rememeber.

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[emoji3516] This for sure. Funny that the x2 method made that happen... But what do I know. [emoji2369]



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Build Thread - Adventures of Fiona - https://wayalife.com/showthread.php?t=47407
 
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