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Unread 02-28-2012, 09:03 AM   #1
David_M
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JKU's on 37's (Tire Pressure)

What tire pressure are you all running to get even tread wear? I know about the chalk test and plan to use it. I just wanted to find an average PSI as a starting point.

Thanks, David M

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Unread 02-28-2012, 10:45 AM   #2
99on35s
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I am running 28 in my trail grapplers!!!
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Unread 02-28-2012, 07:32 PM   #3
sieg
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Soooo many variables. Tire width, tire ply rating, rim width, rim dia...... But my 2dr, with 10 ply, Toyo Open Country 13.50's on 9 by 17 rims, I run 28 front 25 rear.
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Unread 02-28-2012, 08:34 PM   #4
SoK66
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With KM2s after trying everything from 25 to 37 psi I found the best by far on highway is 35psi. Best handling. most even wear. Off road I can run them at 10 psi without beadlocks. I was quite surprised at first, but the weight of the rig (mine comes in at 5100 lbs) and the soft sidewalls of the KM2s seems to be the reason they need some serious pressure.
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Unread 02-28-2012, 09:01 PM   #5
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I'm running 25 on the road. Sometimes down to 10 on the trails.


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Unread 02-29-2012, 03:31 AM   #6
SubAtomicGenius
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Tires are all different, JK weight different, etc. Too many variables. Solution: find a straight, open road and do a chalk test: chalk up tread, drive a bit, observe chalk wear. Takes time, but it's the only way to find out the proper pressure for your rig.

Wear in the middle: pressure too high.

Wear on edges, pressure too low.

Wear even across tread face: pressure just right.


If you don't have time to do that, you can air your tires and look at the contact on the road while you're doing it. Same principle, just not "dynamic" - so you'll have to check a few times after you go out for a run. Generally, big tires need less than factory tire pressure, around 28 psi would be a good starting point. Wide tread tires have a tendancy to balloon out in the middle of the tread at higher pressures, and cause uneven tread wear in the center.

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Unread 02-29-2012, 08:24 AM   #7
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On my stock Rubi muds I found that it runs the best at 37.
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Unread 02-29-2012, 08:39 AM   #8
David_M
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Thanks for all the replies. I do plan to run the chalk test. What lead me to this question was that I recently bought my '07 JKUR a few week ago. This past week I took it apart to regear and noticed the tire pressure seemed high. I checked and to my surprise they were set to about 37-38 PSI. They are 37" Toyo Open Country M/T tires on 17" Walker Evans wheels. That seemed extremely high to me but the tread wear wasn't that bad. The tires have about 1/2 tread left and maybe a little uneven, less tread in the middle but not bad. I thought maybe it's just that these things are heavier than what I was used to with my '99 TJ on 35's.

I'll post back after chalk test on my findings...
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