Tire pressure advice

  1. AnARcHy

    AnARcHy Well-Known Member

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    I have Cooper AT3 XLT 275 70 18 tires on my 18 JLU. The dealer has them inflated to 50 psi, and that seems excessive to me. Any suggestions for correct pressure?
     
  2. DesertsJL

    DesertsJL Well-Known Member

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    Way too high. At most they should be 37 as is recommended by Jeep, or slightly lower based on the slightly larger size. That must ride like a tank at 50psi.
     
  3. OP
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    AnARcHy

    AnARcHy Well-Known Member

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    It actually doesn’t ride bad. They are 10 ply tires, but I’m concerned about tire wear. I read posts about doing the chalk test, but don’t really have a good place to do that. Was hoping to find out what others are running in similar tires.
     
  4. DesertsJL

    DesertsJL Well-Known Member

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    I ran my 33’s at the recommended pressure of 37psi. I lowered my 35’s down to 30. I’m putting 37’s on in a few days and will likely run 28psi or so depending on how even the “chalk test” wear pattern shows. Your tires should measure out 33.7 or so based on the tire calculator. Given that they are also a heavy 10 ply, if it were me, I’d start around 35 and adjust from there. But it’s entirely up to you to find that sweet spot that you like.
     
  5. beaups

    beaups Well-Known Member

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    You don't need chalk to know 50psi is way too high. Even the 37 on the placard is likely a bit high for those tires.
     
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  6. OP
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    AnARcHy

    AnARcHy Well-Known Member

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    I’ll drop them to 35 tomorrow and see how it handles. If I can find a good place to do the chalk test, I will do that. Thanks for the info!
     
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    AnARcHy

    AnARcHy Well-Known Member

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    The tires are rated to 80 psi. I used to own a Dodge Ram 2500 Cummins, and those were the type of tires I ran on it, so I know they are way too much for the weight of my Jeep. I just needed some advice on where to start for the tire pressure. Thanks for the reply!
     
  8. DesertsJL

    DesertsJL Well-Known Member

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    I use my driveway and roll back and forth a few times, but any good smooth section of concrete will do it. You don’t need to drive a long distance in order to see how the chalk is wearing off.
     
  9. Kluk Ztopolovky

    Kluk Ztopolovky Well-Known Member

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    Tires are an important component of the overall suspension system on any vehicle . Correctly inflated tires absorb most of the road impact and by keeping your tires over pressured you are not extending the lifespan of your shock , bolt joints and all the rest of the suspension set up plus you are getting bumpy hard ride.. I rather keep my tire pressure gently under pressurized than too high.
     
  10. WranglerMan

    WranglerMan Well-Known Member

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    Do a chalk test or 10% rule but as stated 50# is way to high
     
  11. blnewt

    blnewt Well-Known Member

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    I run my 10 ply Pats at 30 psi, seems to be the sweet spot for these tires.
     
  12. NewJLU2019

    NewJLU2019 Well-Known Member

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    A friend at 4 Wheel Parts installed my E-rated BFG 275/70R/18 KO2's 33,s BFG Tech says 41 PSI. He had me drive home and feel how the 41 PSI rode and then lower to 34 PSI. Much softer ride at 34 PSI, that's what I keep now.
     
  13. jeepdabest

    jeepdabest Well-Known Member

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    10% rule?
     
  14. WranglerMan

    WranglerMan Well-Known Member

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    yes 10% rule.....basically you can either use the TPMS sensors or a tire gage but obviously the TPMS display is easier but you observe cold air pressure by either means and then drive for 20-30 mins and a good speed to warm the tires which in turn raise the air pressure and the goal is to not go above 10% of the cold psi reading

    Here is an explanation of a bike tire but the concept is the same http://www.allendesigns.com/personal/TenPercentRule.htm

    I just chalk test mine and it’s very close to 10% and I get very even contact
     
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