BFG KO2 LT285/70R/17 Tire Pressure (once and for all)

[Mr._Bill]

Thanks everyone...I must say, I'm even more pissed at Costco.

Just remember that Costco is there to provide goods in quantity so the price is lower for members. I would not expect them to be the best source for custom tires and wheels.

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[brianinca]

PV=NRT is Boyle's Law, pal! ??

You have it right. KO2 are one of a few standard Jeep options so using the door sticker should steer you right. Just note that that is cold tire pressure and its not unusual for the pressure to increase into the low to mid 40's depending on how warm the air inside gets when driving.

Edit: in Scuba we know it as Charles' Law

 

[Ohio JKU]

Your Costco guy is an idiot.

There isnt a single reputable tire shop that will tell you to run near/at max inflation for every day driving.

I bought tires at Costco once, long time ago and will never do it again.

I get no kick backs, but I recommend you find the best price for the tire you want, then go to discount tire. They actually have a clue as to what they are doing.

PS good luck getting Costco to sell/mount a tire larger than factory. They’ll tell you it’s dangerous and not recommended.

i talked to the Costco guy once and figured out that was not where I’d be getting tires ever. I like Costco but not for tires or anything cars.

 

[Ohio JKU]

I’ve been experimenting on a set of copper st maxx on my jku. They are a load rated tire and ride stiff if anywhere above 40 psi,
I’m running them at 33 and it’ much better

 

[brianinca]

Don't feel badly. Tire changers have a low bar to get hired, it should be an entry level position. People with potential move up to bigger and better.

I had the "manager" of the Firestone tire shop tell me I was risking life and limb by putting 31x10.5R15's on my old 98 Explorer. I had swapped to BFG AT's two months after we bought it, the Firestone tires hydroplaned on the freeway where they should have had no problem. I stuck them in the shed.

Three years later I turned them in for $$$ on the horrible recall, practically brand new. I got a bit testy with this DF telling me how it was with tires, and explained his shitty ass brand name store must hire like they engineer their tires. He quit jabbering at that point.

I'll never own a Bridgestone or Firestone tire again, ever. Costco is where you know what you want and you tell them to do X, Y and Z, whether TV's, computers or tires.

Thanks everyone. It's so frustrating...3 separate occasions they said that. I went yesterday since my WARM pressure was at 58!!! They only lowered it to 48.

They said KO2s, specifically, need to be close to that 50 psi mark. I told them I've researched and have always thought that was high.

They are Load Class C, and I would think door sticker is the way to go. I was told since it's a Light Truck...you need that high pressure.

I'll just air them down myself...I just hope I didn't lose any tread life.

 

[DocMike]

If you go with Discount, they are a forum sponsor. PM and they will cut you a deal . I also had them price beat what I found on Amazon.

Thanks everyone...I must say, I'm even more pissed at Costco.

 

[ShadowsPapa]

Normally my local Chevy dealer will beat anyone's price. This time my Jeep dealer matched them. The Chevy dealer is where I got the hard-to-find RWL tires for my 70 and they beat Big O, Discount tire, all of 'em and did a great job mounting them on rare expensive original wheels.
Odd to say it but I trust that Chevy dealer for tires more than most tire places around here.
The Jeep dealer did a heck of a job matching the best internet price I could find.
Costco is clear across the county and always swamped beyond belief. I don't like going there because it's like some Bianca concert or something is always going on (whoever she is)
I worked in one of those places while in college to help pay my way - it's the job I walked out of one night, literally, walked out, got my truck, loaded my tools, drove away and never said a word. I was sick of the stuff I saw going on and refused the boss's orders which I knew could lead to a horrible disaster for a family on vacation. I just could not do it. Sell sell sell, they make squat, they must sell xx per month, etc. it's crazy. I've seen it from the inside - no way I could work in such a place and feel good about it.

 

[mmatthie]

Price was right for me at the time so be it. I aired down already to 36...must smoother ride. Thanks again everyone

 

[stingrey]

PV=NRT is Boyle's Law, pal! ??

Charles' law states that the gas should occupy more space when heated, but a tire does not expand very much. This causes the tire pressure to be higher when warm. Consequently, measuring tire pressure when the tire is warm will give you the false impression that you have filled your tires with too much air.

 

[ShadowsPapa]

PV=NRT is Boyle's Law, pal! ??

No, PV=nRT is the Ideal Gas Law and is a combination of Boyle's law, Charles's law and others.

Boyle's law states that the pressure of a gas increases as the volume of the container or chamber decreases. Pressure is inversely proportional to the volume

Charles's law states that gases tend to expand when their temperature increases.

The ideal gas law -> PV=nRT

 

[stingrey]

No, PV=nRT is the Ideal Gas Law and is a combination of Boyle's law, Charles's law and others.

Boyle's law states that the pressure of a gas increases as the volume of the container or chamber decreases. Pressure is inversely proportional to the volume

Charles's law states that gases tend to expand when their temperature increases.

The ideal gas law -> PV=nRT

Boyle's law is why we are taught don't hold your breath diving or why I release air from BC and drysuit as I ascend. Atmospheres are in play.
'Breath Or Your Lungs Explode Stupid'

Charles' law is why I am disappointed to only find 3200psi in my 3442psi tank that cools the air inside when it hits the water.

 

[ShadowsPapa]

Boyle's law is why we are taught don't hold your breath diving or why I release air from BC and drysuit as I ascend. Atmospheres are in play.
'Breath Or Your Lungs Explode Stupid'

Charles' law is why I am disappointed to only find 3200psi in my 3442psi tank that cools the air inside when it hits the water.

Don't forget the nitrogen bubbles........

You bring up a funny point - my wife freaks out the first time the temps dive to 10 degrees and she wants to drive her Jeep and she sees the tire pressure is only 31 or 32 and they are supposed to be 36. I try to explain - you lose roughly (depending on tire size ) 1 pound of pressure for every 10 degree drop (and sometimes more than 1 on some tires).
If they are filled at 60 degrees to 36 and it's is now 10 degrees out, you have "lost" 4 or 5 psi. She INSISTS I do something about it - FIX IT.

 

[stingrey]

Don't forget the nitrogen bubbles........

You bring up a funny point - my wife freaks out the first time the temps dive to 10 degrees and she wants to drive her Jeep and she sees the tire pressure is only 31 or 32 and they are supposed to be 36. I try to explain - you lose roughly (depending on tire size ) 1 pound of pressure for every 10 degree drop (and sometimes more than 1 on some tires).
If they are filled at 60 degrees to 36 and it's is now 10 degrees out, you have "lost" 4 or 5 psi. She INSISTS I do something about it - FIX IT.

Is she asking you to "Fix Physics" or just buy smaller tires

 

[ShadowsPapa]

Is she asking you to "Fix Physics" or just buy smaller tires

I tried to explain "you cannot change the laws of physics" but it didn't help. She didn't care about the science. So playing Star Trek's Scotty, I fixed it for her - and when Dad died I grabbed his big old air compressor to set up in the garage right behind where she parks her Jeep. Now I don't have to tell her - ok, run it down to the shop and I'll "fix it".
I should paint a sign on that compressor - "Barbara's Compressor" or something like that.

 

[Giljr572]

I've been using Tire Pressure Calculator (tiresize.com) to give me a better idea of the pressure I should be running in my KO2. I haven't done a chalk test yet, but I'm planning to do one to confirm. So based on that I've been running my KO2 at 39 psi. That is to achieve the same load capacity as the OEM Bridgestone Dueller that the Max Tow is equipped with from factory. I could likely run my tires lower when I'm not at capacity, either load wise or towing, hence why I need to do that chalk test. And of course I "air down" when I'm offroad, it makes a big difference comfort and traction wise.

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