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Yes, I know, but I did search...

I have 18" wheels, which requires me to get LT tires in the 10 ply variety...my question really is, do I inflate the tires to the same pressures as I would the typical 6 ply tires? I currently have 275/70R18 BFG KO tires, and am looking to get a set of 285/75R18 DuraTracs.

I've got the current KOs at 24 psi, which seems to give the best ride/wear for what I have. The ride is comparable to the 35x12.5x15 MTs on my old TJ.
 

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You won't find many Wrangler owners with 18" wheel sizes or running 10 ply tires so it's understandable you didn't find any info. Most of us run 15" (me) or 17".
 

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How is the wear pattern on your current tires at that PSI? Tire mfgs rate the pressure for the load built to carry. Auto engineers determine the "BEST" air pressure via testing and it is posted on the vehicle label on the drivers door / door jam. "BEST" psi is what the vehicle is certified with DOT/ EPA / Gov't. Once an owner starts modifying then it is the owner's responsibility on what PSI works for their use and comfort. Candidly the ole Chalk Test is a good starting point.
 

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Candidly the ole Chalk Test is a good starting point.
The chalk test is commonly recommended but it is often best as a tool to cause your tires to be underinflated... often severely underinflated. People without a clue what an acceptable/good air pressure is will often keep letting air out until the chalk is wearing off evenly across the entire tread which is incorrect. Rarely should the entire tread be on the ground.

For most, using the chalk test will result in an underinflated tire... no matter how good it sounds when you hear or read about it.
 

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I was going to ask the same question as I am getting new tires installed next week. I run 285/70R17's, so would 30 psi be about right? I am getting P rated tires instead of LT, if that matters, and I honestly have no idea how to determine these things.
 

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I was going to ask the same question as I am getting new tires installed next week. I run 285/70R17's, so would 30 psi be about right? I am getting P rated tires instead of LT, if that matters, and I honestly have no idea how to determine these things.
The P designates a passenger vehicle (4 ply) not a HD truck (6-10 ply). I have run the Falken 285/70R17s for several years on JKUs.. keeping them at 32-33 psi on the street; with non-stock wheels & dropped to 18 when off roading. BTW these are very close to 33inch tall and wider. Be sure to have the installer check for rubbing (have them show to you how they check).
 

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Thank you. I am getting the Wildpeak AT3W and I have a 4" lift on my TJ. Are you meaning they may rub on a stock Jeep or even with one with a lift?
 

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The P designates a passenger vehicle (4 ply) not a HD truck (6-10 ply). I have run the Falken 285/70R17s for several years on JKUs.. keeping them at 32-33 psi on the street; with non-stock wheels & dropped to 18 when off roading. BTW these are very close to 33inch tall and wider. Be sure to have the installer check for rubbing (have them show to you how they check).
18 psi is not even aired down, you can safely take it lower to 12 psi which is where airing down starts helping. Don't be afraid to air down more. Before getting bead lock wheels 11 years ago I regularly aired my 33's then 35's to 8 psi for my local trails. Nope never lost a bead.
 

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Discussion Starter #11
How is the wear pattern on your current tires at that PSI? Tire mfgs rate the pressure for the load built to carry. Auto engineers determine the "BEST" air pressure via testing and it is posted on the vehicle label on the drivers door / door jam. "BEST" psi is what the vehicle is certified with DOT/ EPA / Gov't. Once an owner starts modifying then it is the owner's responsibility on what PSI works for their use and comfort. Candidly the ole Chalk Test is a good starting point.
The wear pattern seems to be fine. And the ride is not that bad, considering the tires are 10 ply. I've got a set of 35x12.5x15 MTs but I do like the looks of the wheels that were on the Jeep when I bought it. The mileage difference between the two sets of tires is minor, and I'm geared for 35" tires. For now, I'll stick with the 24 PSI, and see how it works out. I'll be taking it on a 500 mile round trip on Tuesday, and I'll see how it does, then.
 

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I'm currently running BFG LT255/75R17 KM2s (Mud-Terrain) on my TJ. What pressures would you guys recommend for street and aired down?
 

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Discussion Starter #13
That's basically a 32" tire...so 28 to 30 PSI should be in the ball park.

You should be able to air down to 10 to 12 PSI without much issue.
 
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