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Old 11-03-2021, 08:42 PM   #1
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Trailer tire air pressure

Is inflating to my tire’s max air pressure(65psi) at 90 degrees outside the same as inflating to 65 psi at 60 degrees?
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Old 11-03-2021, 08:53 PM   #2
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No, but you're supposed to inflate them at ambient air temp. It's normal to need more air when it's cold out. That's why you check them often. 65psi at 99 degrees experts the same amount of pressure on the tire at zero.. the air shrinks which is why the pressure goes down.
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Old 11-20-2021, 07:50 AM   #3
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Simple answer is yes... 65 psi at 90 degrees is the same as 65 psi at 60 degrees. Measured pressure is measured pressure regardless of the air temperature. What you are really asking about is air density. Colder air is more dense than hot air. As the temperature increases, so does the pressure and vice versa. As matman said, thats why you service them to 65 psi at ambient air temperature and continue to monitor as outside air temperature changes and so does tire pressure.
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Old 11-20-2021, 08:02 AM   #4
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90°F is about 5% warmer than 60°F since temperature comparisons have to be measured in degrees Kelvin.

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Old 11-20-2021, 12:13 PM   #5
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Originally Posted by Chuck_S View Post
90°F is about 5% warmer than 60°F since temperature comparisons have to be measured in degrees Kelvin.

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A somewhat bizarre statement.
Fahrenheit to Fahrenheit, period.
Nobody I know of translates from one measurement system to another when making comparisons.
If I am comparing feet to feet in measurements, I don't care a rat's patootie about metric equivalents.
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Old 11-20-2021, 06:37 PM   #6
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90°F is, of course, 30°F warmer than 60°F but so what? it's not significant -- only 5%. Not enough to affect anything.

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Old 11-20-2021, 07:59 PM   #7
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Originally Posted by Boomerweps View Post
A somewhat bizarre statement.
Fahrenheit to Fahrenheit, period.
Nobody I know of translates from one measurement system to another when making comparisons.
If I am comparing feet to feet in measurements, I don't care a rat's patootie about metric equivalents.
It's actually not bizarre at all if you understand the science behind what he's saying (and if you're not a science nerd, you probably don't, and there's nothing wrong with that). Temperature is actually a measure of molecular movement. And converting to Kelvin is the only true way to compare temperatures. This is very different than measuring distances.

For example, if we compare 1 F to 2 F, is the latter really twice as warm? Is 100 F twice as warm as 50 F? Mathematically, both examples show a doubling of numbers. However, I think we can all agree they don't both show equivocal doubling of temperatures.

However, in measuring distance, the same is not true. 4 ft is twice as long as 2 feet. It doesn't matter what unit of measurement we convert it to, that distance will be twice as long as the other one.

Food for thought.
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Old 11-20-2021, 10:32 PM   #8
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Just put in the sidewall listed max pressure on a cold morning. Perfect. It's not rocket science.
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Old 11-21-2021, 09:14 AM   #9
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Appears my complete post didn't get out of my computer. It should have read:

Pressure is directly related to temperature. 90°F is about 5% warmer than 60°F since temperature comparisons have to be measured in degrees Kelvin.

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Old 11-21-2021, 10:10 AM   #10
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Originally Posted by John1949 View Post
Is inflating to my tire’s max air pressure(65psi) at 90 degrees outside the same as inflating to 65 psi at 60 degrees?

Short and simple answer is Yes, but you want to measure and set pressure at what is considered "cold pressure". Cold pressure is the pressure inside the tire first thing in the morning before the tire has been driven, or ambient temperature has risen. Many tires and even placards on the vehicle/trailer will state cold pressure.

Internal tire pressure will increase during the day as the internal temp of the tire goes up. Manufacturers already have this calculated in. You don't want to let air out during this expansion phase to set the tire to cold pressure. The next morning the pressure will go back to the cold inflation as long as you don't tamper with it during the expansion phase (unless you have a leak or replace the tires)


When I am mounting tires during the heat of the day for customers, I add a little extra air to compensate for the expected pressure drop during the night. What is fun is what has happened this week as our night time temps dropped into the 30"s. Many peoples TPMS lights are coming on and they are going into a panic, thinking they are having leaking tires. They come in wanting me to pull their tires off and find leaks. I give them the price for that or offer the the $1 option to air their tires back up to cold ambient temp pressure. You can figure out which option they take. LOL


Tire rack has a great article explaining this below.

https://www.tirerack.com/tires/tiret....jsp?techid=73

Here are some google pics of vehicle and trailer placards as well as a trailer tire sidewall, which state "COLD pressure" as you can read on them
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Old 11-21-2021, 10:35 AM   #11
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Old 11-21-2021, 10:47 AM   #12
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Agree with ARhappycamper. It's not rocket science. Just put the max tire pressure in before the sun hits the tire early in the morning and go. The pressure goes up as the ambient and road heat them up but that by design. Rolling on an under pressured tire is what will get you in trouble. Trailer tires have very heavy side walls and heat up quickly when under pressured.

Trying to relate this to an airplane's performance is a little much.
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Old 11-21-2021, 10:47 AM   #13
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Originally Posted by John1949 View Post
Is inflating to my tire’s max air pressure(65psi) at 90 degrees outside the same as inflating to 65 psi at 60 degrees?
Yes.
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Old 11-23-2021, 10:44 AM   #14
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Quote:
Originally Posted by ARhappycamper View Post
Just put in the sidewall listed max pressure on a cold morning. Perfect. It's not rocket science.
No, PSI as listed on the placard.
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Old 11-23-2021, 11:24 AM   #15
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No, PSI as listed on the placard.
You are both right.

If stock tires are installed the "placard pressure" and sidewall pressure are almost always the same.

Exception would be if one has installed a load range or two higer. Then the placard pressure is just the minimum pressure if trailer not overloaded.
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Old 11-23-2021, 11:32 AM   #16
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I agree with the majority here saying yes.

Those that remove a pound or two or add a pound or two of air every morning according to the outside ambient temperatures are wasting their time.

I air my tires at the beginning of the season using a known good air gauge and then simply 'monitor' that pressure with my TPMS every time I hitch up. No need to be adding or lowering a pound or two just because it's 15º colder/hotter today than it was yesterday.
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Old 11-25-2021, 01:20 AM   #17
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And just when I thought a tire thread couldnt get any worse so I may as well chime in too.



Upgrade tire load range if possible, check air pressure in the AM, inflate to max pressure stamped on tire, ignore placard. Tire problems solved.
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Old 11-25-2021, 05:18 AM   #18
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Originally Posted by Lins View Post
No, PSI as listed on the placard.
Your camper has a tire placard like a vehicle ? My '21 Rockwood does not, but even so, they are trailer tires. They will be adjusted cold and to the pressure stated on the tires.
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Old 11-25-2021, 07:43 AM   #19
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Originally Posted by TitanMike View Post
You are both right.

If stock tires are installed the "placard pressure" and sidewall pressure are almost always the same.

Exception would be if one has installed a load range or two higer. Then the placard pressure is just the minimum pressure if trailer not overloaded.
Finally a voice of reason. Why people want max PSI in any tire when it isn’t necessary I just don’t understand.

Quote:
Originally Posted by ARhappycamper View Post
Your camper has a tire placard like a vehicle ? My '21 Rockwood does not, but even so, they are trailer tires. They will be adjusted cold and to the pressure stated on the tires.
Every trailer I have seen has one.
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Old 11-25-2021, 09:20 AM   #20
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You should weigh your trailer and adjust air pressure according to the tire manufacturer weight air pressure ratio chart.
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