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Thread: Tire PSI?

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    Tire PSI?

    I've got the stock tires on my 381m which require 110psi.

    I've got a tire pressure monitoring system so I am always aware of the tire PSI.

    During my last trip, it was 100 degrees outside and the tires went up to brushing again 130psi. I wonder how high it will get when the temps get to 115! The tires in the sun were a little bit higher than the ones on the other side of the sun, but overall they were all usually within 123-128psi.

    Is that a normal raise in PSI? I know you are supposed to do 110psi cold, but should I lower the cold psi at all when in HOT days?

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    My "G" rated tires, 110 psi, routinely run 120-122 psi when the temperature outside is 75°-80°, so I think what you're seeing is normal. I wouldn't mess with the pressure.
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    Quote Originally Posted by timelinex View Post
    I've got the stock tires on my 381m which require 110psi.

    I've got a tire pressure monitoring system so I am always aware of the tire PSI.

    During my last trip, it was 100 degrees outside and the tires went up to brushing again 130psi. I wonder how high it will get when the temps get to 115! The tires in the sun were a little bit higher than the ones on the other side of the sun, but overall they were all usually within 123-128psi.

    Is that a normal raise in PSI? I know you are supposed to do 110psi cold, but should I lower the cold psi at all when in HOT days?
    Not uncommon. Speed, temperature, altitude will all affect pressures. The cold temp is what is important.

    FYI, They don't "require" 110 PSI that's just the max. On my 125psi H tires I normally run them around a 105PSI. Thats still good for over 4000lbs a tire. When I had G rated Sailun tires on our old solitude which was lighter I ran them around 95PSI.

    Here is the Sailun inflation chart (there all pretty much the same)
    https://fifthwheelst.com/documents/C...T-Modified.pdf

    2 schools of thought on this. Some believe in running the max is safer. I don't subscribe to that theory but everyone needs to do what they feel most comfortable with.
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    Quote Originally Posted by JKellerJr View Post
    Not uncommon. Speed, temperature, altitude will all affect pressures. The cold temp is what is important.

    FYI, They don't "require" 110 PSI that's just the max. On my 125psi H tires I normally run them around a 105PSI. Thats still good for over 4000lbs a tire. When I had G rated Sailun tires on our old solitude which was lighter I ran them around 95PSI.

    Here is the Sailun inflation chart (there all pretty much the same)
    https://fifthwheelst.com/documents/C...T-Modified.pdf

    2 schools of thought on this. Some believe in running the max is safer. I don't subscribe to that theory but everyone needs to do what they feel most comfortable with.
    OK, so mine are also 4080 MAX at 110psi. My trailer runs about 19kLB, but let's even pretend I am at 20k max. That put's a load of 3,333 on each wheel. According to that chart I shouldn't run any more than 80psi?

    EDIT: And that doesn't even include the fact that a good 15+% of that 20k is on the pin.
    Last edited by timelinex; 06-09-2022 at 04:05 PM.

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    Quote Originally Posted by timelinex View Post
    I've got the stock tires on my 381m which require 110psi.

    I've got a tire pressure monitoring system so I am always aware of the tire PSI.

    During my last trip, it was 100 degrees outside and the tires went up to brushing again 130psi. I wonder how high it will get when the temps get to 115! The tires in the sun were a little bit higher than the ones on the other side of the sun, but overall they were all usually within 123-128psi.

    Is that a normal raise in PSI? I know you are supposed to do 110psi cold, but should I lower the cold psi at all when in HOT days?
    Quote Originally Posted by JKellerJr View Post
    Not uncommon. Speed, temperature, altitude will all affect pressures. The cold temp is what is important.

    FYI, They don't "require" 110 PSI that's just the max. On my 125psi H tires I normally run them around a 105PSI. Thats still good for over 4000lbs a tire. When I had G rated Sailun tires on our old solitude which was lighter I ran them around 95PSI.

    Here is the Sailun inflation chart (there all pretty much the same)
    https://fifthwheelst.com/documents/C...T-Modified.pdf

    2 schools of thought on this. Some believe in running the max is safer. I don't subscribe to that theory but everyone needs to do what they feel most comfortable with.
    I have 110 psi tires on my 310 GK and I inflate them to 105 psi. On my last trip the tires ran around 115 psi according to the TPMS, they also were running relatively cool. I was very pleased with those numbers.
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    If you know your actual weight per wheel (not guessing, but individual wheel weights with a scale), you can find your tire manufacturer's load/inflation chart and follow that.

    Rob
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    Quote Originally Posted by SolarPoweredRV View Post
    I have 110 psi tires on my 310 GK and I inflate them to 105 psi. On my last trip the tires ran around 115 psi according to the TPMS, they also were running relatively cool. I was very pleased with those numbers.
    Interestingly, your tires easily see a good 500lb per tire more weight because you are 2 axles VS my heavier but 3 axle.

    I think I will probably set it to 105psi..... Seems like a overly safe #, while still giving some relief to the very high hot numbers.

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    Quote Originally Posted by timelinex View Post
    I've got the stock tires on my 381m which require 110psi.

    I've got a tire pressure monitoring system so I am always aware of the tire PSI.

    During my last trip, it was 100 degrees outside and the tires went up to brushing again 130psi. I wonder how high it will get when the temps get to 115! The tires in the sun were a little bit higher than the ones on the other side of the sun, but overall they were all usually within 123-128psi.

    Is that a normal raise in PSI? I know you are supposed to do 110psi cold, but should I lower the cold psi at all when in HOT days?
    NO!! The air is your tires cooling system. Lowering the pressure on a "hot" day will make them run hotter.
    Tire pressure is ALWAYS to be set when cold. Yes it will rise as they heat up, but that rise has already been acounted for, when setting the PSI cold
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    I run at the pressure listed on the tire for a couple of reasons. After reading many threads on the subject, along with the normally accompanying links to tire experts, I find that at that pressure I am doing no harm. Too low causes flex in the sidewall, thus heat, which can ruin the tires. My tires will never be worn out before they will need to be replaced simply based on the date code on the tires. I will run them beyond the date code, but not a lot beyond. The tires are generally engineered to take over inflation to a fairly high point, mainly caused by heat and altitude. Also, they should be checked and filled when cold, at ambient temp, ideally at 70 degrees. My 2 cents, which means absolutely nothing except to me...
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    Quote Originally Posted by timelinex View Post
    OK, so mine are also 4080 MAX at 110psi. My trailer runs about 19kLB, but let's even pretend I am at 20k max. That put's a load of 3,333 on each wheel. According to that chart I shouldn't run any more than 80psi?

    EDIT: And that doesn't even include the fact that a good 15+% of that 20k is on the pin.
    Quote Originally Posted by Second Chance View Post
    If you know your actual weight per wheel (not guessing, but individual wheel weights with a scale), you can find your tire manufacturer's load/inflation chart and follow that.

    Rob
    As Rob says, best to know your weights but I tend to go over by a pretty good amount and call it a day.

    The research I've done come mostly from the trucking industry. Tires are engineered to run at certain pressures for certain loads. If your running higher pressures than the actual load your over inflated. Smaller contact patch, uneven wear, stiffer side walls and tread face, etc. Tires do handle over inflation better than under inflation especially under the max rating. But from what I read, over inflation runs a bigger risk of punctures along with more shock transferred through to the rig.

    FWIW

    https://www.trucknews.com/features/i...ire-pressures/

    https://www.truckinginfo.com/153054/the-magic-number
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