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Old 11-13-2014, 10:13 AM
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Procal settings

well today my i got my new wheels and tires installed. so far i was able to program the correct gear ratio, now im up to the tire size.

how the hell can you get a accurate reading of a tire? does anybody know the actual tire size for a 285/70/17 Duratrac?? while i thought they considered 33's my pops and I got a measurement between 31 inchs and 32 inches. ..

So what would be the proper setting for these tires on a Procal ?

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Old 11-13-2014, 10:34 AM   #2
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put a piece of chalk in the tread, then roll fwd slowly and measure the distance between the chalk marks on the ground.

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Old 11-13-2014, 10:36 AM
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put a piece of chalk in the tread, then roll fwd slowly and measure the distance between the chalk marks on the ground.
Thank you for the advice, but where would i come up with a piece of chalk ? Lol
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Old 11-13-2014, 10:40 AM   #4
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I guess I take for granted I have chalk because of my kids. You could put a piece of tape on the tire sidewall with a mark, then another one on the driveway, then roll fwd, then another one on the driveway and measure those.

Or you could tape some string to the tire, roll fwd, wrap the string around and then mark the string and measure that.
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Old 11-13-2014, 10:41 AM   #5
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I guess I take for granted I have chalk because of my kids. You could put a piece of tape on the tire sidewall with a mark, then another one on the driveway, then roll fwd, then another one on the driveway and measure those. Or you could tape some string to the tire, roll fwd, wrap the string around and then mark the string and measure that.
Dollar store has sidewalk chalk - works gear!
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Old 11-13-2014, 10:43 AM   #6
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Dollar store has sidewalk chalk - works gear!
great
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Old 11-13-2014, 10:48 AM   #7
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measure from the ground to the center of the hub and X2 and it will be perfect. I have done this at least a dozen times and that works the best. It was also how the guy who invented the procal told me to do it so I figure if any ones knows it would be Jordan who is the brother of the owner of AEV.
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Old 11-13-2014, 11:08 AM
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measure from the ground to the center of the hub and X2 and it will be perfect. I have done this at least a dozen times and that works the best. It was also how the guy who invented the procal told me to do it so I figure if any ones knows it would be Jordan who is the brother of the owner of AEV.
from the ground to the center of the hub and times 2 ? that would give me the exact size ?
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Old 11-13-2014, 11:10 AM   #9
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from the ground to the center of the hub and times 2 ? that would give me the exact size ?
yes it will give you the number to use to program your speedo with the procal.
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Old 11-13-2014, 11:40 AM   #10
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put a piece of chalk in the tread, then roll fwd slowly and measure the distance between the chalk marks on the ground.
you need diameter, not circumference. Put a straight edge on top of the tire, then measure from the ground to the straight edge. If you measure to the hub and then multiply, you're not taking into consideration compression from weight of the vehicle.
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Old 11-13-2014, 11:54 AM   #11
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Yes, correct. Forget to say divide by pi (3.141592) to get diameter.

I tried measuring from the ground to the middle of our rim, but it's hard to tell exactly where the middle is because it's a logo. If you're off by 1/8, then multiplied by 2, that's a possible 1/4" error.

I guess I could put a piece of tape across the middle of the rim and measure where the exact middle is and mark it and then measure from the ground to that.

IMO, chalk, if you have it handy, is the best and easiest way to get the most accurate measurement.
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Old 11-13-2014, 12:44 PM   #12
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measure from the ground to the center of the hub and X2 and it will be perfect. I have done this at least a dozen times and that works the best. It was also how the guy who invented the procal told me to do it so I figure if any ones knows it would be Jordan who is the brother of the owner of AEV.
This is how I did mine a few weeks ago and it worked perfectly. Just remember that a change in tire pressure will affect this number. If you decide later on to run a lower pressure on the street, remeasure and reprogram as needed.

For example, I was initially running 35 PSI in my 33x12.50x15 General Grabber AT2s. That came to 32.25" for programming purposes. When I lowered to 30 PSI, it became 31.5".

Oh, and make sure to take the measurement at one of the front tires.
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Old 11-13-2014, 01:44 PM   #13
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Math says 31.75 inches. 635 revs per mile divided into 63360 and then divided by 3.1416.
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Old 11-13-2014, 01:49 PM   #14
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Yes, correct. Forget to say divide by pi (3.141592) to get diameter. I tried measuring from the ground to the middle of our rim, but it's hard to tell exactly where the middle is because it's a logo. If you're off by 1/8, then multiplied by 2, that's a possible 1/4" error. I guess I could put a piece of tape across the middle of the rim and measure where the exact middle is and mark it and then measure from the ground to that. IMO, chalk, if you have it handy, is the best and easiest way to get the most accurate measurement.
Ah how quickly (it was a long time ago actually) I've forgotten simple math concepts. I stand corrected. Proceed as though I never chimed in....
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Old 11-13-2014, 02:36 PM
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so now measuring from the bottom to the hub which would be say the center cap is the incorrect way of doing this ?? i wasn't expecting this to be that much of a task.... especially since everyone says procal settings are easy.
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Old 11-13-2014, 02:45 PM   #16
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If you can accurately measure from the ground to the middle of your center cap, then yes, that number times 2 should also work.
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Old 11-13-2014, 02:55 PM   #17
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I went through the whole process of measuring with a string. Long story short, you are better off just to enter in the tire size. When I entered in the measured size, the speedo was off by more than it was before! Whatever you do, check it against a GPS or other method to verify your speedo is accurate.
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Old 11-13-2014, 03:23 PM
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I decided to contact Adrian from DTD. he assisted with helping me purchase my wheels/tires last week. i told him what i was doing and he gave me the actual measurement needed to do so immediately its 32.71 i'll be taking messing with this procal as soon as i hit my lunch break in about 30 mins !!
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Old 11-13-2014, 04:04 PM   #19
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park on a flat surface measure from the center of the hub to the ground and x 2 if the tire manufacturer says the tire is 32.7 then it will probably really be around 31.5" actual measured the way I have explained. If you want it to be dead on. If you don't care if it is a little off then 32.75 will work.

Jordan Harriton invented the procal that is how he says to do it.
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Old 11-13-2014, 05:19 PM
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park on a flat surface measure from the center of the hub to the ground and x 2 if the tire manufacturer says the tire is 32.7 then it will probably really be around 31.5" actual measured the way I have explained. If you want it to be dead on. If you don't care if it is a little off then 32.75 will work.

Jordan Harriton invented the procal that is how he says to do it.
i'll give it one more look tomorrow, just to be on the safe side. i did however have time to program it during lunch at 32.75. when i check tomorrow i'll see how much off it is.

To be quite honest, prior to even programing the tires into the procal, the speedo did not seem that off at all... i figured since i already purchased it, that i might as well use it.
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Old 11-13-2014, 07:09 PM   #21
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I decided to contact Adrian from DTD. he assisted with helping me purchase my wheels/tires last week. i told him what i was doing and he gave me the actual measurement needed to do so immediately its 32.71 i'll be taking messing with this procal as soon as i hit my lunch break in about 30 mins !!
32.7 is the measurement for an unmounted tire. A mounted tire with a proper air pressure is gonna measure less than that. You should measure your tires on the Jeep and enter the actual size into the Procal to get the desired result.
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Old 11-14-2014, 10:47 PM   #22
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i have the same tires. went with 32.25 at 45psi and it is almost spot on. i used the old straight edge and a tape measure, then rounded down a bit. instantly gained back about 2 or 3 mpg in mixed driving.

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