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-   -   Adjust tire pressure for cold weather?? (https://www.irv2.com/forums/f258/adjust-tire-pressure-for-cold-weather-558461.html)

RoadTrip2084 10-25-2021 04:06 PM

Quote:

Originally Posted by BigBillSD (Post 5962648)
I have, but so far only Michelin mentions it. And now that I look on their site for a few minutes, I have not found it. Michelin gave us a handout during an escapees seminar, and theirs said tire pressures should be corrected to 68 degrees on what I remember was an official glossy Michelin handout. Its too bad that this last year I was so bored the first couple months I started purging the house of unneeded crap. All that old paperwork went into the recycle bin. I don't use Michelin's anyway.

I only top up my tires when its around 70 degrees in the morning. They have about 50k miles now, and will be aging out in the next couple years. -Bill

The Caterpillar reference I included back in https://www.irv2.com/forums/f258/adj...ml#post5956845 mentions

"The table shows the correct pressures for tires that are inflated in an area with a temperature
of 18 to 21C (64 to 70F)." So that would be considered the default temp. range for cold tire inflation.

MN_Traveler 10-25-2021 04:44 PM

Quote:

Originally Posted by RoadTrip2084 (Post 5962842)
The Caterpillar reference I included back in https://www.irv2.com/forums/f258/adj...ml#post5956845 mentions

"The table shows the correct pressures for tires that are inflated in an area with a temperature
of 18 to 21C (64 to 70F)." So that would be considered the default temp. range for cold tire inflation.

Im sorry - I do not see an interpretation there that implies that you should then adjust the pressures in the tires at colder temperatures so that if the tires were to hit those "reference" temperatures then their pressures would correspond to the pressures they used at those temperatures.. sorry - it does not make sense (physically and mechanically) that at much colder temperatures you would inflate the tires to a LOWER pressure - which would then be unable to support the load (which has not changed with temperature) without overly flexing. sorry .... but to me that is a totally incorrect, and dangerous, interpretation of what they are saying in that publication.

BigBillSD 10-25-2021 05:39 PM

Quote:

Originally Posted by Kid Gloves (Post 5962728)
Perhaps Michelin punted on the idea of a temperature correction factor after realizing that a large percentage of owners cant figure out how to properly inflate their tires when give the simplest of instructions.


Good Point! It says 120 lbs on my tires, that's the pressure I should run.. Right. :whistling: -Bill

Jacjetlag 10-25-2021 05:58 PM

"All tire manufactures state that you should check your tire pressure in the morning before the vehicle has moved more than a mile."

+++++

That said, colder air is more dense. A tire that is carrying thousands of pounds needs adequate pressure to perform as designed.

If you are too lazy to fill them or just ignorant , it is at your own peril.

https://www.youtube.com/watch?v=aiMIG4phsW4&t=23s

vlamgat 10-25-2021 06:05 PM

Quote:

Originally Posted by Domo (Post 5956658)
No, you don't adjust your pressure during the day. Overinflation changes the profile of your tires and affects performance - at least according to the Michelin folks I've spoken to on three occasions - but some folks don't seem to believe them.

Here's a good read about tires from a manufacturer;

I am surprised that it took so long for your comment's arrival to address the issue of PHYSICS. It seems the prevailing opinions are to forget physics and stick to the number. That air pressure in tires decrease about 1 psi per 10 degrees; and that the recommended pressure is at 20 deg C/68 F means that seeing a tire pressure that was at 65 when the temperature was 68 in the morning and rose to 71 when the out of the sun ambient was at 90 is quite normal. Similarly they will drop from 65 to 62 around freezing. Reinflating them to 65 is over inflating them.

There is a consensus that irrespective of the temperature there is a pressure below which you should not run the tire in order to retain bead integrity and that is recommended by Michelin and Continental ( the only OEMs that I have seen this discussed ) at 75% of the rated temperature.

However this is not an exact science and also one where most of the science is retained by the OEMs to avoid liability. But it does raise the question as to how impaired a tire becomes if the pressure is 5% over or under the tire maximum at maximum weight? I do not think anyone knows, not even the OEMs. So for some this will be a holier than thou life's work to maintain the "perfect" pressure while for others, if it will take a good kick, its ok.

RoadTrip2084 10-25-2021 07:06 PM

Quote:

Originally Posted by MN_Traveler (Post 5962886)
Im sorry - I do not see an interpretation there that implies that you should then adjust the pressures in the tires at colder temperatures so that if the tires were to hit those "reference" temperatures then their pressures would correspond to the pressures they used at those temperatures.. sorry - it does not make sense (physically and mechanically) that at much colder temperatures you would inflate the tires to a LOWER pressure - which would then be unable to support the load (which has not changed with temperature) without overly flexing. sorry .... but to me that is a totally incorrect, and dangerous, interpretation of what they are saying in that publication.

I think you're confused. The chart below the text shows the adjusted cold temp. tire pressure you should use for the equiv. normal cold tire pressure if you're dealing with COLD temps (32f and below). In each case the recommended pressure is higher than the default pressure.

MN_Traveler 10-25-2021 07:28 PM

Quote:

Originally Posted by RoadTrip2084 (Post 5963080)
I think you're confused. The chart below the text shows the adjusted cold temp. tire pressure you should use for the equiv. normal cold tire pressure if you're dealing with COLD temps (32f and below). In each case the recommended pressure is higher than the default pressure.

Ok - apologies. What the manual is saying (and this is a quote) is "tires inflated in a warm shop will be underinflated in cold temperatures". This is correct and makes sense. again - apologies.

What others are saying is exactly the opposite of what the linked manual is saying. THEY are saying that you should always maintain an inflation equivalent to what the tire contents would be (pressure wise) if they were shifted in temperature to some reference temp (like 68F). That is invalid, unsafe, and actually exactly opposite of what the linked manual is saying.

MN_Traveler 10-25-2021 07:37 PM

Quote:

Originally Posted by vlamgat (Post 5962982)
I Similarly they will drop from 65 to 62 around freezing. Reinflating them to 65 is over inflating them.

.

I am not quite positive what you are trying to say .... but if you are saying, as I think you are, that when the temperature is low, that you should NOT reinflate the tires to (as in your example) to, say, 65 .... that is just plain wrong and dangerous. See my just previous posting (where I apologized for misinterpreting what the poster was saying), then go read the quote I give in that posting, then go read the manual that for which that poster gave a link. it explicitly says that tires inflated in a warm shop (say 68F) will be underinflated when taken out into cold/freezing conditions. So ... if you are saying that if you actually have the tires out in freezing conditions, and you are reading a pressure that is below the minimum inflation for the load, that you should NOT reinflate the tires .... That is incorrect.

And to say that the manufacturers do not have any idea of what pressures cause damage to the tires (it is that damage, NOT unseating the bead as you apparently incorrectly claim) - that is also very sorely incorrect.

It is called engineering "testing".

This time I am truly and completely done with this thread.

Cactusbu11 10-25-2021 08:04 PM

Typically how many years can you get out of a tire even if the tread is still good?

Kid Gloves 10-25-2021 08:39 PM

Quote:

Originally Posted by BigBillSD (Post 5962955)
Good Point! It says 120 lbs on my tires, that's the pressure I should run.. Right. :whistling: -Bill

Well heck, if it says 120 right there on the tire, that must be the correct pressure, for you, and everyone else who puts that tire on their vehicle.

Brilliant!

NXR 10-25-2021 10:04 PM

Adjust tire pressure for cold weather??
 
But...when air gets colder it gets more dense and can support more weight. That's the concept of Density Altitude in aviation and why aircraft can take off in a shorter distance when it's cold than what it's hot.

https://www.faasafety.gov/files/gsla...%20branded.pdf

So if colder air is more dense why do we need to add pressure to tires when it gets colder? If the air in a tire truly is what supports the weight, shouldn't more dense air (cold air) be able to support more weight and not less?

Ray

MN_Traveler 10-25-2021 10:59 PM

Quote:

Originally Posted by NXR (Post 5963257)
But...when air gets colder it gets more dense and can support more weight. That's the concept of Density Altitude in aviation and why aircraft can take off in a shorter distance when it's cold than what it's hot.

https://www.faasafety.gov/files/gsla...%20branded.pdf

So if colder air is more dense why do we need to add pressure to tires when it gets colder? If the air in a tire truly is what supports the weight, shouldn't more dense air (cold air) be able to support more weight and not less?

Ray

Ok .... for a clearly serious, and actually very insightful question, I will try to answer .... because it might help cut through some of the misinformation on this thread.

Ray - this is actually a really good question - and the answer is that this is really mixing two very different aspects of physics.

A plane wing flies because of two things: the curved top of the wing which produces lower pressure on the top of the wing than on the bottom (the Bernoulli effect - which is is a pressure thing and has nothing to do with density), and the angle of attack of the wing (where, when the front of the wing is tilted upward and the wing pushed forward, air hitting the bottom of the wing is deflected downward, which exerts an upward force on the wing (newtons third law - when an object exerts a force on another object, the second object exerts an equal and opposit force on the first - strictly a density/mass thing, and has nothing to do with pressure).

Your density altitude thing is mostly a result of the angle of attack of a wing allowing it to "push" downward on the air - the denser (colder) the air, the stronger the upward force (because the air molecules are closer together, and the wing pushes more molecules downward for a given amount of forward motion .... kind of like throwing downward two baseballs versus one ... it takes more force to throw down two of them.

Inside a tire, there is no such "pushing" of air, and so its density becomes a non-issue. The ONLY thing acting inside a tire is the pressure the air exerts on the tread, walls, and rim of the tire. This works because a given pressure pushing on the tire "stiffens" the tire, and limits how much the sidewalls of the tire will deflect for a given load. If the pressure is lower, the tire sidewalls are not held stiffly in place, and can deflect more (very much like a very underinflated balloon is easy to squeeze and deform, but a highly inflated balloon is very stiff, and difficult to deform - it can support more weight without deforming.

To understand pressure - you really need to understand statistical thermodynamics .... but the simple explanation is that pressure is the result of lots and lots of gas molecules hitting the inside of the tire .... it is nothing more than that. It is the summation over time of many, many small "balls" (molecules) each with very very small mass and momentum hitting a wall. So .... the fewer the number of molecules inside the tire (like letting air out of the tire), the fewer will be hitting the wall in a given time, and the pressure is lower (the opposite is true when you add air to the tire.

As for temperature - it turns out that the speed a gas molecule flies through space is directly dependent on the temperature (the maxwell-boltzmann distribution). So for a tire with a certain amount of air in it, if the temperature goes down, the speed that the gas molecules are moving at goes down, and they each hit the inside of the tire with less momentum - and the pressure (and thus stiffness of the tire) goes down - for a given amount of weight on the tire, the tire deforms more. The tire may technically be supporting the weight, but upon each revolution it deforms more than if it were supported by a higher pressure - and it is this ongoing increased amount of deformation that causes increased stress and damage to the tire.

Kid Gloves 10-26-2021 06:40 AM

Thanks for coming back. Again.

So, would an airplane be able to take off in an even shorter distance, if it were inside a tire filled with compressed air?

MN_Traveler 10-26-2021 07:54 AM

Quote:

Originally Posted by Kid Gloves (Post 5963472)
Thanks for coming back. Again.



So, would an airplane be able to take off in an even shorter distance, if it were inside a tire filled with compressed air?



Lol. I guess. Would take a pretty big tire though [emoji4]


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