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Your tire is 598 revolutions per mile. Tire size is 33.7. Put that number into your programmer.
My tires measure about 34.4 when measure with a yardstick and a level at the tallest top of tire. Am I wrong?
I don't use measurements anymore, I prefer the results with a GPS speedo.
 

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Discussion Starter #62
I don't use measurements anymore, I prefer the results with a GPS speedo.


So what would I do to figure out proper tire size for programmer with GPS?


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I don't use measurements anymore, I prefer the results with a GPS speedo.
I use highway mile markers over 10 miles and compare to the odometer.
 

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So what would I do to figure out proper tire size for programmer with GPS?
I use the Speedometer app on my smartphone. Set the tires in the programmer to a ballpark number. Say 33.00 for "35's". Then drive.... If my speedo reads faster than the actual GPS speed, I pull over and adjust the tire size down to 32.75 for example. If my speedo reads slower than the GPS, I pull over and adjust my tire size larger... Repeat. In just a couple of miles, and a few stops for adjustment, my speedo and GPS will match exactly.

I use 60 mph as my baseline. And for what it's worth, my tire size is set at 32.75 with 35's and it reads exact at 60.

Make sense?
 

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Discussion Starter #65
I use the Speedometer app on my smartphone. Set the tires in the programmer to a ballpark number. Say 33.00 for "35's". Then drive.... If my speedo reads faster than the actual GPS speed, I pull over and adjust the tire size down to 32.75 for example. If my speedo reads slower than the GPS, I pull over and adjust my tire size larger... Repeat. In just a couple of miles, and a few stops for adjustment, my speedo and GPS will match exactly.



I use 60 mph as my baseline. And for what it's worth, my tire size is set at 32.75 with 35's and it reads exact at 60.



Make sense?


Yes. My speedo matches my waze.


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Are the Yukon gears about the best out there for quiet and life. Are they as good as Dana/Spicer. Getting this done one time only.
 

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Are the Yukon gears about the best out there for quiet and life. Are they as good as Dana/Spicer. Getting this done one time only.
Dana Spicer is the gold standard. I'm running Yukon as the shop that did my regear has had 1 gear warranty in thousands of gear jobs with Yukon.
 

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My tires measure about 34.4 when measure with a yardstick and a level at the tallest top of tire. Am I wrong?

Well, yes. If the mfg says they rotate 598 times in a mile just do the math.

63,360 inches in a mile. Pi 3.14159.

63,360/598=105.953

105.953/3.14159=33.7259

Your tire is a 33.7
 

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I am a click away from having the Dana 4.56's done. Just got to schedule it.
 

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I am a click away from having the Dana 4.56's done. Just got to schedule it.
I would seriously consider 4.88's for LA traffic.
 

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Discussion Starter #72
Well, yes. If the mfg says they rotate 598 times in a mile just do the math.

63,360 inches in a mile. Pi 3.14159.

63,360/598=105.953

105.953/3.14159=33.7259

Your tire is a 33.7


I suck at math! But speedometer is correct.

Thanks


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Are the Yukon gears about the best out there for quiet and life. Are they as good as Dana/Spicer. Getting this done one time only.


I did the Yukon 5.38 gears on my 08. Put well over 100,000 on them before I traded the Jeep in. No problems and still quiet after all that mileage.


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Tire manufacturer would be my uneducated guess.

That's what I thought.
That means you can't apply it to all situations. It would be a 'ballpark' number only



A tire manufacturer works from a particular standard (max pressure, max weight). As a result that number would change depending on the weight of the vehicle and the air pressure of the tire.


You would probably gain more accuracy simply by measuring radius (center axle to ground).


Don't measure diameter. It will give you a false number.
 

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Just GPS it guys, much easier.... :)

And I agree, radius of axle center to ground x2 would be the closest number.
 

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To determine tire size for the programmer, I measure from the garage floor to the center of my wheel and then double it. The thought being that the tire is under load for the duration of a revolution. This has provided the most accurate result when verifying with GPS.
 

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the guy who actually invented the procal (Jordan the brother of the founder and owner of AEV and incredibly smart guy) told me in person to measure from the ground to the center of the wheel and yes X2. Now you need to take a couple things in to account AEV specifically says to run 28-30 psi with their lifts and they are basing this measurement on an 8.5" wide rim. I have AEV rims and run 28psi and my speedo is spot on. He also said to start on the low side ie if your measurement is 33" might try 32.75" to begin with, now this is a stumper but instead of moving up only a 1/4" at a time move up an inch program it and then come back down to where you want and program it again.
 
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