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Tireman9 10-26-2021 11:41 AM

Quote:

Originally Posted by PBK Images (Post 5961673)
My understanding from Michelin is that the standard temp they use is 68F. Assuming that my OAT in the morning is 45F, and my front tires (with the weight that I am carrying) is recommended to be a minimum of 117psi. But I could go up to the max limit of the tire and/or wheel, say 130PSI, my inflation goal at 45F will be the minimum (117 PSI). Why? Because I know that the OAT will increase during the day and the tire temp will increase as I drive. Just using common sense. If it is much colder, say, 35F, and I know that after a mile or two the tires will heat up to 45F and then continue heating, I might "cheat" a pound or two and inflate to 115psi to avoid higher psi at operating temps. Everyone has their own thoughts.


While I know that Michelin has some ideas that are not supported by all other tire companies, I sincerely believe that either you are mis-remembereing or initially misunderstood that statement about 68F being some "standard". Sorry to hear that you lost the document as I would consider that "ground-breaking" information if accurate. Is it possible that the document was from a tire dealer and not Michelin corporate?

Tireman9 10-26-2021 11:43 AM

Quote:

Originally Posted by Kid Gloves (Post 5961795)
There is no standard temperature. Where did you find a load and inflation chart that recommends 117psi? You need to round up in 5psi increments to 120psi. Why would you ever inflate to less than the recommended minimum cold pressure?

Higher psi at operating temperatures is normal. Itís physics, itís inescapable. You are not using common sense.




Correct.

Tireman9 10-26-2021 11:45 AM

Quote:

Originally Posted by NXR (Post 5961803)
The minimum pressure I use is 90 PSI. "Minimum" as in not underinflated at all and coincidentally is also the inside DOT sticker. So 90 PSI can fully support the GAWR of each axle.

I usually set the tires to 98 or so to give me some temperature margin.

When I leave Florida at the end of March I bring all of the tires up to 100 PSI from the 95 PSI or so they usually are at that time.

When I arrive in Cleveland, OH and the temps are in the low 40's to high 30's, the next morning the tires are sitting at 90 PSI or a tad more.

It works for me.

We'll be leaving here in late December for Florida so I'll have the tires here at about 95 PSI. Whatever they are when we get to Florida will be where they stay unless somehow they are over the maximum sidewall cold pressure of 110 PSI. That has not happened yet.

I put air in the tires twice a year, when we leave Florida in early Spring and in the late Fall before we leave northern Ohio.

FWIW,

Ray


I live near Akron so understand. Your plan and approach is reasonable.:thumb::thumb::thumb::thumb:

Tireman9 10-26-2021 12:00 PM

Quote:

Originally Posted by BigBillSD (Post 5962319)
Why wouldn't the tire pressure recommendations be to a corrected temperature like maybe 70 degrees? Using a TPMS allows you to see your tire pressures rise within a minute or so of starting to drive. My tires usually run at the same (130lbs) pressure when its 60 degrees outside and at 110 degrees outside, and they start at 115lbs cold. I have watched that many times driving from San Diego over toward Yuma on the way out of town. Changing the pressures every morning due to the outside temperature sounds more like an old wives tale.. (or more appropriately a senile engineer's tale) Or, we have always done it that way mentality. Within a few minutes your tires are hot. Maybe we are saying that its those first couple miles that kill the tire, as after that the pressure & tire temp rise pretty fast. -Bill

PS. This should "heat" up the discussion..


I have never advocated changing tire pressure each morning. I do strongly support the adjustment of inflation that is lower than 110% of what is needed to support your measured load on the tires on the heaver end of an axle.
Having "cold" morning pressure that is greater than 120% of your "set pressure would be when I could possibly consider a change but only if the predicted temperature for the day was + 30F or more than it is where you are located AND you are already at 120% of your set pressure.
In my experience which includes 3 cross country trips and temperature ranges from 24F to 98F I do not ever recall bleeding pressure off.


So I am now expecting someone that travels to Alaska in February and Death valley in August to come up with a situation that is outside of my general guidelines. But lets get real. Most people travel in the lower 49 when temperatures range from 40s to maybe 100F. That should mean your morning pressure might change by 12%. :thumb:



Lets try this... Set your morning pressure to between 105% and 120% of the minimum needed to support the measured load. I bet if you do that you would only be adjusting cold pressure a couple times a year.:dance:

jrd22 10-26-2021 12:36 PM

After a life time of driving trucks of all sizes (CDL-A) both local and long distance the one thing that has saved countless tires for me has been to check the temperature of each tire when hot (after driving, when stopped for fuel, etc) by touching all of them. If one is hotter than the norm, it's probably low or has some other problem. It's just a habit for me (and most good truck drivers) now to check all the tires when I stop for fuel (a quick walk around). Just caught a low tire the other day in MT, picked up a nail in a trailer tire, and had it repaired before heading over the mountain passes. I always set tires to the max psi indicated on the sidewall cold when hauling heavy and have usually had great tire life out of them. You can over think some stuff.

Tireman9 10-26-2021 01:16 PM

Quote:

Originally Posted by inkahauts (Post 5962601)
If you really want to worry less about fluctuations in pressure you could find a place that could drain all the air from your tires and replace it with nitrogen air. It will have far less fluctuations between cold pressure and driving pressure. And then only add nitrogen air when it needs any more at some point.




How would you "drain" all the air out? Sucking a vacuum in a tire will simply de-seat it.
There is almost no meaningful difference if the Pressure/Temperature change between dry air (78% N2) and a purged tire with 93% N2.

Ray,IN 10-26-2021 08:17 PM

Quote:

Originally Posted by Tireman9 (Post 5963963)
How would you "drain" all the air out? Sucking a vacuum in a tire will simply de-seat it.
There is almost no meaningful difference if the Pressure/Temperature change between dry air (78% N2) and a purged tire with 93% N2.


I'm sure happy you joined in this thread Roger! It's incredible what some folks come up with.

Kid Gloves 10-26-2021 08:22 PM

Just imagine the great achievements that might be possible if the creative minds were to focus on something other than ways to reinvent the tire inflation guidelines provided by the tire manufacturers.

Ramrod 10-27-2021 05:46 AM

Quote:

Originally Posted by MN_Traveler (Post 5956552)
Oh my. This will be a lively discussion. The "safe" answer is never run them at all, even for a few minutes, if they are below their minimum. This is exactly why i add 10 psi above the charts ... so on cold mornings i dont have to go out and inflate them.

I have no doubt though that other members here will say otherwise.

I for one disagree with you. Never over inflate your tires. Very dangerous. Set them every travel day to the recommended cold pressure. It only takes a few minutes each time.

Ramrod 10-27-2021 05:51 AM

Quote:

Originally Posted by MN_Traveler (Post 5963299)
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.

BRAVO !!!!!!!!

Chargerman 10-27-2021 06:04 AM

Adjust tire pressure for cold weather??
 
Adding 10psi over the recommended inflation pressure is not over inflating the tire unless it exceeds the tires maximum pressure on the sidewall. Remember, the chart lists the minimum pressure required to support a given load. Going above that is basically adding some cushion. The only thing that may be sacrificed when increasing above the recommended pressure is the ride.

Ray,IN 10-27-2021 09:59 AM

Quote:

Originally Posted by Ramrod (Post 5964736)
I for one disagree with you. Never over inflate your tires. Very dangerous. Set them every travel day to the recommended cold pressure. It only takes a few minutes each time.


Please link to one instance where overinflation from load/inflation charts caused tire failure, Then links to tire failures from underinflation/overloading.

Ray,IN 10-27-2021 10:05 AM

Quote:

Originally Posted by Kid Gloves (Post 5964526)
Just imagine the great achievements that might be possible if the creative minds were to focus on something other than ways to reinvent the tire inflation guidelines provided by the tire manufacturers.

Add to that, the information from The USDOT and NHTSA, and Tire mfgrs association.

Kid Gloves 10-27-2021 10:34 AM

Quote:

Originally Posted by Chargerman (Post 5964750)
Adding 10psi over the recommended inflation pressure is not over inflating the tire unless it exceeds the tires maximum pressure on the sidewall. Remember, the chart lists the minimum pressure required to support a given load. Going above that is basically adding some cushion. The only thing that may be sacrificed when increasing above the recommended pressure is the ride.

I would suggest that owners consider a +10% recommendation rather than a +10psi recommendation.

On the heavier coaches that require 90psi or more,+10ps is certainly an appropriate consideration. An additional 10psi may be a bit more than necessary on a rig that has a cold pressure recommendation of 65psi. And a passenger car may only require the addition of 3psi.

I am aware that this is a Class A discussion.

MN_Traveler 10-27-2021 10:43 AM

Quote:

Originally Posted by Kid Gloves (Post 5965051)
I would suggest that owners consider a +10% recommendation rather than a +10psi recommendation.



On the heavier coaches that require 90psi or more,+10ps is certainly an appropriate consideration. An additional 10psi may be a bit more than necessary on a rig that has a cold pressure recommendation of 65psi. And a passenger car may only require the addition of 3psi.



I am aware that this is a Class A discussion.



All my tires are close enough to 100 psi that 10 psi IS 10% (or close to it) . Just me being lazy and not doing the math.. you could also call it an "engineering approximation". [emoji4]

Kid Gloves 10-27-2021 10:51 AM

Quote:

Originally Posted by MN_Traveler (Post 5965071)
All my tires are close enough to 100 psi that 10 psi IS 10% (or close to it) . Just me being lazy and not doing the math.. you could also call it an "engineering approximation". [emoji4]

In your case, that works out. It may not for others.

That was the message I was attempting to get across.

MN_Traveler 10-27-2021 11:14 AM

Quote:

Originally Posted by Kid Gloves (Post 5965085)
In your case, that works out. It may not for others.

That was the message I was attempting to get across.

LOL - I was really mostly joking and trying to insert some humor. agreed that if one's pressures were much lower it would probably pay to be more exact...

Tireman9 10-27-2021 04:30 PM

Quote:

Originally Posted by MN_Traveler (Post 5963299)
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.




From a tire design engineer... Good explanation of "why" it is the air that "supports" the load. Thanks.

Tireman9 10-27-2021 04:33 PM

Quote:

Originally Posted by Ramrod (Post 5964736)
I for one disagree with you. Never over inflate your tires. Very dangerous. Set them every travel day to the recommended cold pressure. It only takes a few minutes each time.




In theory yes. BUT in reality too much work wor the average person and the normal day to day pressure changes of 1 to 3 psi "cold" isn't that significant.


If you make it too much work, and some would consider changing inflation daily way too much work given we can't get most to check inflation once every few months, too much work would discourage some from ever checking psi.

Tireman9 10-27-2021 04:35 PM

Quote:

Originally Posted by Chargerman (Post 5964750)
Adding 10psi over the recommended inflation pressure is not over inflating the tire unless it exceeds the tires maximum pressure on the sidewall. Remember, the chart lists the minimum pressure required to support a given load. Going above that is basically adding some cushion. The only thing that may be sacrificed when increasing above the recommended pressure is the ride.






Yup:dance::thumb:

TommyHarris 10-28-2021 04:29 PM

So, I see some who are saying to set pressure to max cold pressure recommended, and others talk about “minimum +10%”…I’m confused.

2020 Fleetwood Pace Arrow 33D

Ray,IN 10-28-2021 09:36 PM

Quote:

Originally Posted by 1Motorhome (Post 5956521)
I recently noticed my cold pressure has decreased in all tires (by TPMS) by almost 7 pounds in the mornings with temps in the 40's. But within 10 driving miles they are back to normal pressure.
My question is, should I add more air at cold ambient temps to bring pressure to cold normal settings?

I really hope the pages of replies have helped, especially replies from Tireman9, who is a retired tire engineer.

Ray,IN 10-28-2021 09:38 PM

Quote:

Originally Posted by TommyHarris (Post 5966681)
So, I see some who are saying to set pressure to max cold pressure recommended, and others talk about ďminimum +10%ĒÖIím confused.

2020 Fleetwood Pace Arrow 33D

I would follow Tireman9 's advice, being a retired tire engineer he knows more than any of us irv2.com members.

Tireman9 10-29-2021 10:19 AM

Quote:

Originally Posted by TommyHarris (Post 5966681)
So, I see some who are saying to set pressure to max cold pressure recommended, and others talk about ďminimum +10%ĒÖIím confused.

2020 Fleetwood Pace Arrow 33D


Starting at the end.


Assuming you know the actual load on each tire from your measurement on a scale (ya I know about assuming but every RV owner has been told at least once to learn their actual loading).
You take the load on the heavy end of an axle as there are almost zero percent RVs with the load exactly at 50/50% side to side.


The load number is then found in the Load/Inflation charts for your size tire and you go up (to the right) till you find a block with at least or more load than what you measured on the scale. NEVER go lower than your scale reading. DO NOT average the reading from each end of the axle weight measurement. DO NOT try and calculate a pressure between the 5 psi increments. Then look up in the chart to find the PSI. That is the MINIMUM inflation you should ever run in the tires on that axle.


I suggest you add 10% to that inflation number to offer some "protection" in case the temperature drops. If you have added my recommended 10%, you will probably see that you do not have to add air every day the temperature drops 10 degrees.


RVs have Certification labels AKA Tire Placards that have tire size, type, Load range and inflation numbers. They also have GAWR which is the MAXIMUM load you should ever have on that axle. The RV company is required, by DOT to post on the sticker, an inflation number that is sufficient to support 100% of the GAWR. RVIA (a standards organization sticker on the side of your RV now requires inflation level good enough to support 110% of GAWR, which is better than the DOT requirement) Because of these load capabilities most RV companies select the smallest (lowest cost for them) tire that can just barely meed these requirements. The result of this purchasing decision is that you will need to inflate your tires to the level needed to support the tire's MAXIMUM load capacity which is the number on the sidewall of the tire.


Side issue. The wording on the tire sidewall is confusing. The reality of what it means is that any given tire has a MAXIMUM load capacity and an inflation (minimum) required to support that load. What is not printed on the tire sidewall is the fact that there is no increase in inflation that will result in that tire ever being capable of supporting more load. Therefore the "max inflation":facepalm: wording that was decided upon by some committee 50 years ago.

jadatis 11-01-2021 07:46 AM

Made my ( to) long story about why I think pressure as to be higher cold at 100degrF then at 70 degrF.

Here it is.

Why pressure should be calculated back to 70 degrF.

That pressure of tires is related to the temperature of gascompound in tire, is fact.

But that for instance you need for 100 degrF ambiŽnt temperature higher cold filled pressure, then for 70 degrF, and for 40 degrF can do with lower pressure then for 70 degrF, is a conclusion I took, and is the discussion here.

I am going to explain how I came to this conclusion.

I once had a long telephone call with a man from Vredestein , and he explained that goal of pressure determination and maxload of tire, is to not overheat them.

He explained that the molecule-structure of natural rubber can be compared to spagetti, and if you push your nail in it the print remains . Then the ď spagetty-strings" slide over each other.

Tires are vulcanised at the end, and this makes sulfurbridges between the ď spagetti ď wich makes the rubber flexible, so when you push your nail in it , the print directly dissapears, the rubber goes back to its original shape.

The rubber needs a certain amount of sulfurbridges, but to much makes the rubber hard, and if then bending of the rubbber, by the deflection and flexing back every cycle, gives small cracks, wich dont disapear ( logical)

When rubbers temperature goes above a critical temperature, to many sulfur bridges are created,and rubber hardens. Wich temperature this is I dont know, but the vulcanising proces is at 170 degrC is 340 degrF.

Rest is my Einstein way of thinking, and because my average IQ is probly half of that of Mr Einstein, change is 2ce as much that my theory is proven wrong once.

The temperature of the rubber is created by the balance between heating up a second and cooling down a second.

When you begin driving at cold pressure in ambiŽnt temperature of 70degrF, in-and out-side-tire air and all the rubber of tire is 70 degrF. The heat-transport then is zero.
In basics Maxload is calculated for reference-pressure ( E-load 80 psi) and reference-speed ( P- and LT tires mostly 99mph/160kmph) so when you drive that speed constant with maxload on tire and reference-pressure cold filled in tire, no overheating of any part of tire. I practice a bit more complicated.

Yust for the example say you then drive 99mph constant speed, with referencepressure of 80psi ( E-load) and maxload on tire. In the beginning cooling down is marginal, because temperaturedifferences between rubber of tire and in and outside tire gascompound is still zero, but driving long enaugh rubber yust below its critical temperature in the middle of the thickest parts of tire, and at the edges , where rubber meats the gascompound, lets say 300 degrF.
Inside tire gascompound I state as 140degrF. Outside the tire always air 70 degrF.

Then temperature difference between edges of rubber and inside tire gascompound 300-140=160 degrF., and between outside tire air 300-70=230 degrF. Also the inside tire gascompound is cooled down mostly trough the rimm to the air outside the tire with only 140-70= 70 degr temperature difference so 160/70 = 2.28 times as much cooling down by the better transport trough the metal rimm.
So coolingfactor then inside tire 160/230=70% of outside tire. In and outside tire Together 230+160=390 degrF
The rubber temperature then stays in balance ,so heating up factor also 390 degrF.

But the deflection , so heatproduction a second at that speed, then is lesser then at cold pressure, because temp in tire 140degrF, wich gives higher pressure. 80 psi filled at 70 degrF becomes 92.9 psi at 140 degrF.

Now situation ambiŽnt temp 100 degr F.
Temp of rubber still max 300degrF.
Temperaturedifference rubber and outside tire air 300-100= 200 degrF
Temperaturedifference rubber and inside tire gascompound 70% of outside 200= 140 degrF.
Together200+140=340 degrF worth of cooling capacity
So temperature inside the tire 300-140= 160degrF.

So at 70degrF ambiŽnt temperature 390degrF worth of cooling capacity.
At 100degrF ambiŽnt temperature 340degrF worth of cooling capacity.
This has to be compensated by lesser heatproduction a second by lesser deflection of tire is 340/390=87.2 % of the heatproduction at 70degrF ambiŽnt temperature.
Now if 80psi filled at 70degrF
At 100F/85.4psi
At 140F/ 92.5psi
At 160F/ 96.1psi
So 92.5/96.1=96.25% of the surface on the ground then at 70degr F driving 99mph with maxload on tire. Rule of tumb I determined gives 0.9625^2= 92.64 times the deflection . If heatproduction goes lineair with the deflection ( I hope and not more), this gives 92.64% of the heatproduction.

Cooling down is 87.2% , so heating up is even still more then cooling down, if 300degrF is the critical temperature of rubber .
If you then lower the 85.4psi cold pressure at 100degrF ambiŽnt temperature to 80psi, as is stated to be allowed because cold filled is at ambiŽnt temperature, the pressure becomes at 160degrF 90.2psi instead of 96.1psi ,wich gives more deflection so heatproduction a second, so rubber of tire temperature goes above 300degrF, and it hardens and cracks.
In fact , because at 100degr heating up factor is 92.64% and cooling down factor is 87.2% at 100degrF ambiŽnt temperature of the 70degrF situation, you should even pump the tires up a little to give lesser heatproduction a second., so heating up factor goes also to 87.2

Now ambient temp 40degrF.
Outside tire 300- 40= 260 degrF worth of cooling down factor.
Inside tire 300- ( 70% of 260= 182 degrF)= 118 degrF inside tire gascompound
So cooling down factor 260+182= 442 degrF
This is 442/390= 113.3% of coolingdown factor then at 70 degrF.
Then at 40 degrF 80psi filled at 70 degrF becomes
74.6 psi cold and at 118 degrF inside tire temp 88.6 psi
92.5psi/88.6 psi = 1.044 times more surface on ground gives 1.044^2= 1.09x more heatproduction.

So when colder tires rubber stays cooler then 300degrF when driving 99mph with maxload and reference-pressure on tire. So for safety not needed to fill up the cold pressure of 74.6 psi to 80 psi , with difference to hot temps, that you may do so for riding quality and fuell saving.

So I think the lists for filling higher at 70 degrF in a heated garage , to get the 80 psi in this example at for instance 20 degrF is because at those extreme cold ambiŽnt temperatures the deflection gets to much so for instance snake-bite.
Then its not anymore to prefent overheating, but for riding -quality.

jacwjames 11-01-2021 08:17 AM

I like the KISS method.


I use a TPMS to monitor pressure and temp.

I set the tire pressure ~10 psi higher then the placard says. I know this may give a "rougher" ride but my coach seems to handle it, drives straight and true, tire wear is minimal if any.

I visually inspect my tires often.


I do not move the coach until the TPMS shows all good, most of the time I just leave it on, but will shut if off if parked longer periods. I've trained my wife to do the same thing.


I have set low pressure and high temp alarms.


While traveling this summer I went from ~90F temps >>> +100F >>> to 45F temps at which point my low pressure alarm sounded on one tire. So I went around and adjusted all the tires. All good rest of trip. I carry a small pancake compressor to use, use just had to start generator.


Now at homes temps start dipping again. Getting ready to go on a trip so I plugged in the TPMS. Got a low pressure alarm again so I went around and adjusted all the pressures.





I know it can be tedious to get the pressures equalized but what I found is that if I over inflate slightly ~2 psi and let the tires site for a while and monitor the TPMS and then one by one I will unscrew the pressure sensor to bleed air, doing this several times to get the same pressure.

Easier then trying to unscrew sensor add air, screw back in sensor and check repeat!!!!

Kid Gloves 11-01-2021 08:35 AM

Option 1: Follow manufacturer recommended guidance for tire inflation.

Option 2: Spend hours compiling useless information.

MN_Traveler 11-01-2021 08:42 AM

Quote:

Originally Posted by jadatis (Post 5970807)
Made my ( to) long story about why I think pressure as to be higher cold at 100degrF then at 70 degrF.



Here it is.



Why pressure should be calculated back to 70 degrF.



That pressure of tires is related to the temperature of gascompound in tire, is fact.



But that for instance you need for 100 degrF ambiŽnt temperature higher cold filled pressure, then for 70 degrF, and for 40 degrF can do with lower pressure then for 70 degrF, is a conclusion I took, and is the discussion here.



I am going to explain how I came to this conclusion.



I once had a long telephone call with a man from Vredestein , and he explained that goal of pressure determination and maxload of tire, is to not overheat them.



He explained that the molecule-structure of natural rubber can be compared to spagetti, and if you push your nail in it the print remains . Then the ď spagetty-strings" slide over each other.



Tires are vulcanised at the end, and this makes sulfurbridges between the ď spagetti ď wich makes the rubber flexible, so when you push your nail in it , the print directly dissapears, the rubber goes back to its original shape.



The rubber needs a certain amount of sulfurbridges, but to much makes the rubber hard, and if then bending of the rubbber, by the deflection and flexing back every cycle, gives small cracks, wich dont disapear ( logical)



When rubbers temperature goes above a critical temperature, to many sulfur bridges are created,and rubber hardens. Wich temperature this is I dont know, but the vulcanising proces is at 170 degrC is 340 degrF.



Rest is my Einstein way of thinking, and because my average IQ is probly half of that of Mr Einstein, change is 2ce as much that my theory is proven wrong once.



The temperature of the rubber is created by the balance between heating up a second and cooling down a second.



When you begin driving at cold pressure in ambiŽnt temperature of 70degrF, in-and out-side-tire air and all the rubber of tire is 70 degrF. The heat-transport then is zero.

In basics Maxload is calculated for reference-pressure ( E-load 80 psi) and reference-speed ( P- and LT tires mostly 99mph/160kmph) so when you drive that speed constant with maxload on tire and reference-pressure cold filled in tire, no overheating of any part of tire. I practice a bit more complicated.



Yust for the example say you then drive 99mph constant speed, with referencepressure of 80psi ( E-load) and maxload on tire. In the beginning cooling down is marginal, because temperaturedifferences between rubber of tire and in and outside tire gascompound is still zero, but driving long enaugh rubber yust below its critical temperature in the middle of the thickest parts of tire, and at the edges , where rubber meats the gascompound, lets say 300 degrF.

Inside tire gascompound I state as 140degrF. Outside the tire always air 70 degrF.



Then temperature difference between edges of rubber and inside tire gascompound 300-140=160 degrF., and between outside tire air 300-70=230 degrF. Also the inside tire gascompound is cooled down mostly trough the rimm to the air outside the tire with only 140-70= 70 degr temperature difference so 160/70 = 2.28 times as much cooling down by the better transport trough the metal rimm.

So coolingfactor then inside tire 160/230=70% of outside tire. In and outside tire Together 230+160=390 degrF

The rubber temperature then stays in balance ,so heating up factor also 390 degrF.



But the deflection , so heatproduction a second at that speed, then is lesser then at cold pressure, because temp in tire 140degrF, wich gives higher pressure. 80 psi filled at 70 degrF becomes 92.9 psi at 140 degrF.



Now situation ambiŽnt temp 100 degr F.

Temp of rubber still max 300degrF.

Temperaturedifference rubber and outside tire air 300-100= 200 degrF

Temperaturedifference rubber and inside tire gascompound 70% of outside 200= 140 degrF.

Together200+140=340 degrF worth of cooling capacity

So temperature inside the tire 300-140= 160degrF.



So at 70degrF ambiŽnt temperature 390degrF worth of cooling capacity.

At 100degrF ambiŽnt temperature 340degrF worth of cooling capacity.

This has to be compensated by lesser heatproduction a second by lesser deflection of tire is 340/390=87.2 % of the heatproduction at 70degrF ambiŽnt temperature.

Now if 80psi filled at 70degrF

At 100F/85.4psi

At 140F/ 92.5psi

At 160F/ 96.1psi

So 92.5/96.1=96.25% of the surface on the ground then at 70degr F driving 99mph with maxload on tire. Rule of tumb I determined gives 0.9625^2= 92.64 times the deflection . If heatproduction goes lineair with the deflection ( I hope and not more), this gives 92.64% of the heatproduction.



Cooling down is 87.2% , so heating up is even still more then cooling down, if 300degrF is the critical temperature of rubber .

If you then lower the 85.4psi cold pressure at 100degrF ambiŽnt temperature to 80psi, as is stated to be allowed because cold filled is at ambiŽnt temperature, the pressure becomes at 160degrF 90.2psi instead of 96.1psi ,wich gives more deflection so heatproduction a second, so rubber of tire temperature goes above 300degrF, and it hardens and cracks.

In fact , because at 100degr heating up factor is 92.64% and cooling down factor is 87.2% at 100degrF ambiŽnt temperature of the 70degrF situation, you should even pump the tires up a little to give lesser heatproduction a second., so heating up factor goes also to 87.2



Now ambient temp 40degrF.

Outside tire 300- 40= 260 degrF worth of cooling down factor.

Inside tire 300- ( 70% of 260= 182 degrF)= 118 degrF inside tire gascompound

So cooling down factor 260+182= 442 degrF

This is 442/390= 113.3% of coolingdown factor then at 70 degrF.

Then at 40 degrF 80psi filled at 70 degrF becomes

74.6 psi cold and at 118 degrF inside tire temp 88.6 psi

92.5psi/88.6 psi = 1.044 times more surface on ground gives 1.044^2= 1.09x more heatproduction.



So when colder tires rubber stays cooler then 300degrF when driving 99mph with maxload and reference-pressure on tire. So for safety not needed to fill up the cold pressure of 74.6 psi to 80 psi , with difference to hot temps, that you may do so for riding quality and fuell saving.



So I think the lists for filling higher at 70 degrF in a heated garage , to get the 80 psi in this example at for instance 20 degrF is because at those extreme cold ambiŽnt temperatures the deflection gets to much so for instance snake-bite.

Then its not anymore to prefent overheating, but for riding -quality.



I appreciate your effort to give a writeup of your thinking ... but there unfortunately is a lot of things that are incorrect in this.

First is the assumption that temperature is the *only* thing that degrades tires. This is not the case. Tires are not only rubber ... they also have steel plys encased in the rubber. Excess flexing (like when the tire is low on pressure) stresses the materials at the boundaries between steel and rubber, and decreases the "bond" between them, thus weakening the tire. This is more a mechanical thing than a thermal thing.

Second, your analysis seems to rely on an assumption that either part of the tire must be running at vulcanization temperatures, and that reaching vulcanization temperatures is necessary to create damage to the tire. Both of these are incorrect. Vulcanization temperatures are HOT. if a tire reached those temps, you would be seeing smoke. Tires just dont get that hot. Also, thermal damage (which is not just damage to the sulfer bridges, but actually is mostly damage/breaking of the "strings" between the sulfer bridges) occurs at any temperature, but is accellerated more as temperatures go up. There is no "magic" temperature where damage starts ... but the hotter they get the more damage is done.

I think you are partially correct in that at low ambient temperatures the risk of thermal damage is reduced, but if the tire is underinflated, you still have increased flexure, and thus greatly increased risk of strictly mechanical damage.

Thank you again for your efforts to get your thoughts put down in writing.

jadatis 11-02-2021 03:19 AM

Answer to post #128 right above.

I used the maxload and that vulcanisation temp as extreme example so most likely overheating kind of problems begin at lower rubber temp.

Firs used 280degrF as highest allowed rubber temp, but gave even more difference between heating up and cooling down.

And luckyly we dont drive 99mph with RV , wich keep the tires rubber cooler.

But ST is calculated in maxload so driving 65mph with maxload and reference-pressure, gives that 300degrF ( if thats the critical temp) , the more deflection then is not yet seen as a problem.

But thebpoint I am making is that especially at high AmbiŽnt temperature, you must not fill 80 psi( if determined needed) but higher, and thats the discussion here.

Kid Gloves 11-02-2021 07:20 AM

Quote:

Originally Posted by jadatis (Post 5971813)
Answer to post #128 right above.

I used the maxload and that vulcanisation temp as extreme example so most likely overheating kind of problems begin at lower rubber temp.

Firs used 280degrF as highest allowed rubber temp, but gave even more difference between heating up and cooling down.

And luckyly we dont drive 99mph with RV , wich keep the tires rubber cooler.

But ST is calculated in maxload so driving 65mph with maxload and reference-pressure, gives that 300degrF ( if thats the critical temp) , the more deflection then is not yet seen as a problem.

But thebpoint I am making is that especially at high AmbiŽnt temperature, you must not fill 80 psi( if determined needed) but higher, and thats the discussion here.

What qualifications do you have to make recommendations other than those provided by the tire manufacturers?

jadatis 11-02-2021 08:02 AM

Answer to post #130.

I am yust an amateur in this.
If you follow the official accepted rule of filling fi80 psi if determined right, at ambiŽnt temperature, next can happen.

You leave at a hot morning of 90 degrF , and give tires 80psi cold pressure.
Then driving higher speed, the tires then overheat, to my conclusions.

And that may only happen ZERO times in tires live.

MN_Traveler 11-02-2021 08:49 AM

Jadatis - i dont know if this will do any good, but will try. I have to admit that i have a little trouble understanding you analysis (due to the english translation), but i have tried, and i *think* i understand what you are trying to say. And ... i am afraid your analysis is very flawed.

First, your assessment that heat is lost from the tire directly from the tire to the ambient as well as through the rim (which is correct) is an *additive* "heat loss factor" is incorrect. The processes act in parallel (not additive). There is more wrong with these sets of assumptions regarding how heat is transferred out of the tire, but lets leave it at that.

The second thing i spot is that your assumption of a certain temperature internal to the tire is mathematically flawed. This is not a class on differential equations so i wont go into detail ... but leave it at the statement thatyou do *not* go about understanding a system like this by assuming some internal temperature. In this case doing do has led you to a conclusion that is dangerously wrong.

I applaud you for trying to think about this logically in terms of heat generation and loss of that heat to the ambient, but the approach you have taken is incorrect and misleading

Someone asked your credentials. I will give you mine, so hopefully you are less likely to just dismiss what i said above. I have a PhD in chemical engineering ... with much of my focus (in training and in my career) on heat transport, and very high end computer analysis of heat transport.

Crasher 11-02-2021 08:52 AM

I find it amazing that so much can be said about attaining the correct tire pressure. It's such a simple process. Either inflate to the placard pressure and don't overload the axles, or weigh the wheel positions and inflate according to the load inflation tables, (keeping all tires on an axle equal) that the tire manufacturer has tested to be a safe level. It doesn't get any simpler than that.

757driver 11-02-2021 08:55 AM

Quote:

Originally Posted by Crasher (Post 5972114)
I find it amazing that so much can be said about attaining the correct tire pressure. It's such a simple process. Either inflate to the placard pressure and don't overload the axles, or weigh the wheel positions and inflate according to the load inflation tables, (keeping all tires on an axle equal) that the tire manufacturer has tested to be a safe level. It doesn't get any simpler than that.

Could not agree more. :thumb:

MN_Traveler 11-02-2021 09:39 AM

Quote:

Originally Posted by Crasher (Post 5972114)
I find it amazing that so much can be said about attaining the correct tire pressure. It's such a simple process. Either inflate to the placard pressure and don't overload the axles, or weigh the wheel positions and inflate according to the load inflation tables, (keeping all tires on an axle equal) that the tire manufacturer has tested to be a safe level. It doesn't get any simpler than that.



Why take a simple approach when you can complicate things beyond all recognition? [emoji4]

(For the record, i weigh, add 10%, and use the same pressure on both sides of an axel)

jadatis 11-02-2021 12:07 PM

Quote:

Originally Posted by 1Motorhome (Post 5956521)
I recently noticed my cold pressure has decreased in all tires (by TPMS) by almost 7 pounds in the mornings with temps in the 40's. But within 10 driving miles they are back to normal pressure.
My question is, should I add more air at cold ambient temps to bring pressure to cold normal settings?

I quoted the original question, to show that this topic is all about , what to do at cold ambiŽnt temperature.
My conclusion is do nothing, but more impotant is that you dont lower pressure at high ambiŽnt temperature.

Its important to determine the needed pressure with reserve, but that is not the question in this topic.

But my idea is that 2ce as much temperature-difference gives 2ce as much cooling down. Am I wrong in that.
And in the end all the heat is transported to the outside air, the rimm is only a 2nd barriŽre.
For this reason it would not be wise to make rimms of Carbon. Does not transport the heat as good as iron or alloy.

jadatis 11-02-2021 01:17 PM

1 Attachment(s)
MN-Traveler wrote " Vulcanization temperatures are HOT. if a tire reached those temps, you would be seeing smoke.

Tried it out.
Own a electric paint-stripper wich you can read and tune the temperature.
Took an inner tire of bicicle, and began at 170 degrC= 338 degrF, and heated the tire at one spot,
Became a bit whitisch but stil flexable afterward.

So at 190 degrF , nothing , took larger steps
At 300 degrF/572 degrF still nothing happened, and inpatiantly went direct to 400grC/ 752 degrF, and YES , a bit smoke and smell , and rubberbubbled up and surface harder and afterward cracks. Made picture of it.

But still I think the 170 degrC/ 338 degrF must not be reached. Mayby 130 degrC= 266degrF is not good for the tire.

Kid Gloves 11-02-2021 02:30 PM

Quote:

Originally Posted by jadatis (Post 5972378)
MN-Traveler wrote " Vulcanization temperatures are HOT. if a tire reached those temps, you would be seeing smoke.

Tried it out.
Own a electric paint-stripper wich you can read and tune the temperature.
Took an inner tire of bicicle, and began at 170 degrC= 338 degrF, and heated the tire at one spot,
Became a bit whitisch but stil flexable afterward.

So at 190 degrF , nothing , took larger steps
At 300 degrF/572 degrF still nothing happened, and inpatiantly went direct to 400grC/ 752 degrF, and YES , a bit smoke and smell , and rubberbubbled up and surface harder and afterward cracks. Made picture of it.

But still I think the 170 degrC/ 338 degrF must not be reached. Mayby 130 degrC= 266degrF is not good for the tire.

Have you ever asked your buddy at Vredestein what the highest temperature is that heís ever seen on a tire? Specifically, one operated within the stated load and speed ratings.

All this stuff has been figured out, by professionals.

Follow their recommendations. Itís pointless to keep trying to reinvent the wheel.

Engineers on this forum have repeatedly mentioned the flaws in your theories. Will you ever heed their advice?

MN_Traveler 11-02-2021 05:12 PM

Jadatis - one final, not quite so delicate, attempt to sway you from your theory. Here in Minnesota it is getting colder. Just today, the "Low Tire" pressure warning went off in my car. Not because the tire lost air, but because the pressure is getting lower because the temperature is getting colder (all of the tires are showing lower pressures). IF your theory is valid, then please explain to all of us here why, many, many VERY smart scientists and engineers have not designed the pressure sensors that are nowadays installed in almost every car manufactured to .... correct for temperature and NOT issue a "low tire" warning just because the temperature has gone down????? The reason is because your theories are not only just plain wrong, they are uninformed and DANGEROUSLY wrong.

To all others reading this thread - please think very carefully before you give credence to the theories and advice offered on this subject by Jadatis.

2cyber71 11-02-2021 05:25 PM

My normal cold pressure by my weights is 105 all around my Horizon.
I left Pennsylvania last December 26th my pressure was 99
Kept my speed at about 55-60 on the interstate until I got to 103 and then picked up to 65. By the time I got to Virginia I was running 115 and tire temps were normal all the way. By the time I got to Florida I was running 120
Never put air in or took it out.
Drove back north and by the time I got home I was running 105.

jadatis 11-03-2021 05:31 AM

Quote:

Originally Posted by MN_Traveler (Post 5972640)
Jadatis - one final, not quite so delicate, attempt to sway you from your theory. Here in Minnesota it is getting colder. Just today, the "Low Tire" pressure warning went off in my car. Not because the tire lost air, but because the pressure is getting lower because the temperature is getting colder (all of the tires are showing lower pressures). IF your theory is valid, then please explain to all of us here why, many, many VERY smart scientists and engineers have not designed the pressure sensors that are nowadays installed in almost every car manufactured to .... correct for temperature and NOT issue a "low tire" warning just because the temperature has gone down????? The reason is because your theories are not only just plain wrong, they are uninformed and DANGEROUSLY wrong.

To all others reading this thread - please think very carefully before you give credence to the theories and advice offered on this subject by Jadatis.

I have read from motorbikes that had tmps , wich gave pressure calculated back to 18degrC/65degrF, and they must be using temperature reading of internal sensor.
The calculation then happened in the recever-unit.
But even an internal sensor does not give exact the temperature of the inside tire gascompound, but better then external sensors.

Forgot the name , but the writer behind you describes that he monitored the pressure during trip and changing ambiŽnt temperature, but did not worry about it and did not change the cold pressure. And that is to opinion the right way, better then maniacaly adjusting it every time.
I wonder if the valves wont wear out faster, from all this.

Kid Gloves 11-03-2021 07:34 AM

Quote:

Originally Posted by 2cyber71 (Post 5972661)
My normal cold pressure by my weights is 105 all around my Horizon.
I left Pennsylvania last December 26th my pressure was 99
Kept my speed at about 55-60 on the interstate until I got to 103 and then picked up to 65. By the time I got to Virginia I was running 115 and tire temps were normal all the way. By the time I got to Florida I was running 120
Never put air in or took it out.
Drove back north and by the time I got home I was running 105.

Best practice would have been to inflate to 105 (your normal cold pressure) prior to leaving Pennsylvania in December. As far as determining correct pressures, what your pressure “gets to” while driving is irrelevant.

Was there a difference in ambient temperature between December and the time that you returned to Pennsylvania? A 30-40F difference would explain why the cold pressure increased from 99 to 105. That’s a perfect example of why pressure should be set when tires are cold.

Kid Gloves 11-03-2021 02:33 PM

Quote:

Originally Posted by jadatis (Post 5973037)
Forgot the name , but the writer behind you describes that he monitored the pressure during trip and changing ambiŽnt temperature, but did not worry about it and did not change the cold pressure. And that is to opinion the right way, better then maniacaly adjusting it every time.
I wonder if the valves wont wear out faster, from all this.

Someone inflating their tires incorrectly and then not worrying about it does not validate your theory.

It might support your opinion. If thatís what you are seeking, youíve come to the right place. The internet provides plenty of opportunities to find someone who will agree with you, even if youíre both wrong.

How can you be given so much information that dispels your theories, yet remain so unwilling to accept any of that information?

wolfe10 11-03-2021 02:43 PM

OK, ambient temperature went from 90 to 60 degrees F this week (yes, in Florida) Stopped and added air to the tires.


Yes, the tires DID read the IDEAL GAS LAW, and followed it. So, I followed it as well. Cold PSI (before driving was too low-- added air).


Have done that every fall/winter since I owned a vehicle (about the same time I had to learn the IDEAL GAS LAW). See, higher education (in the sciences) IS worth something.

RoadTrip2084 11-04-2021 07:59 AM

Quote:

Originally Posted by wolfe10 (Post 5973619)
OK, ambient temperature went from 90 to 60 degrees F this week (yes, in Florida) Stopped and added air to the tires.


Yes, the tires DID read the IDEAL GAS LAW, and followed it. So, I followed it as well. Cold PSI (before driving was too low-- added air).


Have done that every fall/winter since I owned a vehicle (about the same time I had to learn the IDEAL GAS LAW). See, higher education (in the sciences) IS worth something.

Yes, this is the way. :)

jadatis 11-04-2021 08:24 AM

1 Attachment(s)
MN-traveler wrote in reacton to my long explantion next
I think you are partially correct in that at low ambient temperatures the risk of thermal damage is reduced, but if the tire is underinflated, you still have increased flexure, and thus greatly increased risk of strictly mechanical damage.

Now for ST tires they calculate maxload in the bigger sises for 65mph wich gives to my calculation , if realy maxload on tire and reference-pressure in tire 1.38 x the deflection then a LT tire.
The 1.1 x in my example for 40 degrF against 70 degrF. Is then much less.

OK many ST gave tire-failure, but I still think that was because of overheating, and not the exessive flexing.


Also calculated it for european "for trailer use only" tyres, wich calc in maxl for 140kmph/87mph instead of C- tyre( LT- tire) 160kmph/99mph, and it gave 1.14 x deflection , and those are used often enaugh ( but by these eresponcible Europeans ;) ) for 10 years without failure.

On trucktires in Europe almost always additional service descriptions then fi 154L and 156K.
Calculated that back to 1.06x deflection at 110kmph/68mph against deflection for 120kmph/75mph.
And you cant argue that its a different material or construction, because they write it on same tire.

See picture I made about 2 years ago, above the yellow line.

I agree that there is a limit to the more deflection, but 10% more is not it ( to my conclusion for what it is
worth).

jadatis 11-11-2021 09:42 AM

I wonder what all the tire-specialists here, think of my idea to use the higher cold pressure at 100degrF. Example : you determined 80 psi to be right for the axle on a E-load tire.
Then you leave the campground for a long trip in the end of the morning with ambiŽnt temperature 100 degrF. You filled the 80 psi at 70 degrF ambiŽnt temperature.
But then you measure 85.4 psi ( as far as you can measure it that acurate, yust for the example).

What must be done.

1 . Leave it at 85.4 psi cold even if that is above " maximum cold pressure " of tire.?

2. Bring back the pressure to 80 psi, becausse 80 psi has to be filled at ambiŽnt temperature?

My answer you will know, but then again, I dont call myself tire-specialist, only " pigheaded Dutch selfdeclared tyrepressure-specialist "

Kid Gloves 11-11-2021 12:13 PM

Check it again the following morning.

There is no other correct answer.

There are, however, incorrect decisions.

jadatis 11-11-2021 12:36 PM

But the following morning the trip is already done, so possible damage if wrong decided is already done.

Kid Gloves 11-11-2021 03:08 PM

Set it in the morning, then stop thinking about it.

NXR 11-11-2021 11:20 PM

Quote:

Originally Posted by jadatis
But the following morning the trip is already done, so possible damage if wrong decided is already done.

Not even close to accurate. If you're supposed to be at 80 PSI as determined by the actual weighing of the RV and the tire manufacturer's charts (unless these are ST tires which should be inflated to the sidewall pressure when cold) then low pressure is your enemy. A tire that is 20% low is considered to be flat, or 64 PSI in your example.

You may be confused by the pressure molded into the sidewall. That is NOT the maximum pressure the tire can ever see. It is the MINIMUM pressure needed to support the design maximum load weight of the tire.

My motorhome tires do heat up when running and can and do exceed the pressure molded into the sidewall. It's normal and expected and accounted for in the tire design.

Oh, and NEVER let air it of a tire that is not "cold", meaning it has not had direct sun on it and it has not been driven on for hours.

And buy a TPMS.

Ray

Tireman9 11-12-2021 07:56 AM

Quote:

Originally Posted by jadatis (Post 5981902)
I wonder what all the tire-specialists here, think of my idea to use the higher cold pressure at 100degrF. Example : you determined 80 psi to be right for the axle on a E-load tire.
Then you leave the campground for a long trip in the end of the morning with ambiŽnt temperature 100 degrF. You filled the 80 psi at 70 degrF ambiŽnt temperature.
But then you measure 85.4 psi ( as far as you can measure it that acurate, yust for the example).

What must be done.

1 . Leave it at 85.4 psi cold even if that is above " maximum cold pressure " of tire.?

2. Bring back the pressure to 80 psi, becausse 80 psi has to be filled at ambiŽnt temperature?

My answer you will know, but then again, I dont call myself tire-specialist, only " pigheaded Dutch selfdeclared tyrepressure-specialist "




Again you seem to have missed the point.:facepalm: Tire pressure is to be set when tires are at the AMBIENT air temperature outside on the start of a trip.:banghead: No adjustment is needed.:dance:


The only exception would be if you are inflating tires in a heated garage and the temperature is much colder. Example it's -20įF (-29įC) outside and the tires on the vehicle are in a warm building at 65įF (18įC). That would be when you would use a "Cold Inflation adjustment" chart that I published on March 12 2021 in my RVTireSafety blog.

jadatis 11-12-2021 08:33 AM

You seem to miss my point, and yust keep repeating your argument.

Its not always possible to check the pressure in the morning , and even in europe, 1ce a month checking is adviced and before a long trip.

My example was that exeption, checking before a long trip , but then you measure that 85.4 psi.

Then you argue to bring it back to 80 psi, and I argue to keep it at 85.4 psi, even if that is above referencepressure.

My idea is easyer, you dont have to do anything, and to my conclusions the tires run cooler when driving.

Kid Gloves 11-12-2021 08:49 AM

This is hopeless. Iím out.

Ray,IN 11-13-2021 12:49 PM

Quote:

Originally Posted by Kid Gloves (Post 5983096)
This is hopeless. Iím out.

Ya, when people will not heed the advice of a tire design, construction, and forensics engineer. It's time to bail.

MN_Traveler 11-13-2021 01:24 PM

Die thread ... die.....

Crasher 11-13-2021 04:00 PM

About 75 posts ago, I thought that maybe this umpteenth tire pressure thread would die for lack of participation. Guess I was wrong.

MN_Traveler 11-13-2021 04:41 PM

Quote:

Originally Posted by Crasher (Post 5984426)
About 75 posts ago, I thought that maybe this umpteenth tire pressure thread would die for lack of participation. Guess I was wrong.



I think jadatis is going to keep trying to reel people in, unless all just stop trying to respond to him

2cyber71 11-13-2021 04:46 PM

Quote:

Originally Posted by Chargerman (Post 5956560)
Tire pressures should be set cold and this is why adjustment is usually needed as the seasons change. I wouldn’t adjust if you happen to be traveling to a cooler or warmer area temporarily but if your where you’re going to be then you should adjust pressures based on their cold temperature pressure of the tires

This is the answer.
I just adjusted mine because I’m going to Florida in December
I usually run 105 all around, I was down to 95.
Added enough to get back to 105 for the trip.
It might run a bit high in Florida but I can aways take some out, easier than adding.

jadatis 11-18-2021 09:30 AM

https://www.tyresizecalculator.com/t...-in-the-summer

On this page confirmation of my idea.

Quote

If the pressure is measured at +20įC (garage temperature in the morning), tyres should be inflated at recommended manufacturer's tyre pressure (for example, 2.0 bar). If the temperature drops to 0įC, pressure of 1.8 bar should not be increased.

If the outside temperature rose to +40įC pressure of 2.2 bar should not be lowered.
End quote

Given in international standard ( exept America and some other countries) degrC and bar, but the idea stays the same.
And can be that they read my idea once and worked it out. Mailed them to ask what their credentials where on this subject, but did not receve an answer yet.

Mayby its a real Dutch attitude to dare to discuss with the boss.

MN_Traveler 11-18-2021 10:47 AM

Jadatis - you are making a fool of yourself. If you really read and understand the article, you will see that they are making exactly the opposite point of the nonsense you are trying to sell. On top of that, their use of 20C is an EXAMPLE, not a standard.

Dutch attitude??? I have known quite a few people from the Netherlands. In fact, I have sat as an examiner on a PhD exam at Utrecht. The people from the Netherlands are quite, quite intelligent and would not spout the nonsense you keep repeating.

jadatis 11-18-2021 11:25 AM

Quote

If the pressure is measured at +20įC (garage temperature in the morning), tyres should be inflated at recommended manufacturer's tyre pressure (for example, 2.0 bar). If the temperature drops to 0įC, pressure of 1.8 bar should not be increased.

If the outside temperature rose to +40įC pressure of 2.2 bar should not be lowered.
End quote


My opinion is that this quote has no Chinese in it.
It states that the 2.2 bar measured at 40degrC should not be lowered ( to 2.0 bar) . My statement is that you certainly must not lower it to 2.0 bar then.

And the 1.8 bar at 0 degrC ( 32 degrF) should not be increased( but I state that it is allowed for roadhandling and fuelsaving)

So same statement as I give, and not the opposite.

Ray,IN 11-20-2021 09:20 AM

Quote:

Originally Posted by jadatis (Post 5989845)
Quote

If the pressure is measured at +20įC (garage temperature in the morning), tyres should be inflated at recommended manufacturer's tyre pressure (for example, 2.0 bar). If the temperature drops to 0įC, pressure of 1.8 bar should not be increased.

If the outside temperature rose to +40įC pressure of 2.2 bar should not be lowered.
End quote


My opinion is that this quote has no Chinese in it.
It states that the 2.2 bar measured at 40degrC should not be lowered ( to 2.0 bar) . My statement is that you certainly must not lower it to 2.0 bar then.

And the 1.8 bar at 0 degrC ( 32 degrF) should not be increased( but I state that it is allowed for roadhandling and fuelsaving)

So same statement as I give, and not the opposite.

I would agree with your two sentences beginning with IF. Never start out with tire pressure lower than the minimum required for the load.


The article you linked to is wrong about a tire rupturing from excessive air pressure for the scenario it describes.
Here are two articles to read:
https://www.rvtravel.com/rver-concer...sure-increase/
https://www.cartalk.com/content/it-p...ssure-find-out

jadatis 11-20-2021 11:02 AM

2 Attachment(s)
There where 3 ifs, the first 2 in 1 alinea.
But I just picked out of that article , wich comfirmed what I state.

Higher cold pressure then behind AT ( D-load AT 80 psi) was allowed in earlyer days .

Can present you an old document of Michelin in wich up to 40% more cold, and then standing still ( speed zero) 2times the maxload allowed.
Also in that lower pressure for lower speed, down to 20kmph/ 12.5mph) on road, wich gives much more deflection.

Also the ST was allowed 10 psi more cold, so then 90 psi for a AT 80 psi tire. Meanth for 75mph instead of 65, but secretly you can use it for what you want.

In Europe the tyres in the Continental-groop give right behind the service descriptions the referencepressure in psi, and somewhere else on sidewall the "maximum inflation pressure " of 10 psi more. Enlarge the 2 pictures to read it.

And I once read from a tete a tette between Tireman9 and Capriracer that tires have teststandard that they must stand 2 to 3 times the reference-pressure.

If you would fill the tire at 32 degrF / zero degrC with 40% more then reference-pressure ( 1.4 x80 psi = 112psi) and incidentially the temp in tire rises to 212 degrF/ 100degrC, the pressure rises to a smal 2 times reference ( 158.4psi for the AT 80 psi E-load tire) , so yust within the teststandard.

So its not the pressure that destroys the tire but the temperature of tire material ( and not the air inside)

The tire then blows or treath seperates at extreme situation like hot day, but the real cource is overheating long time ago ( my opinion)

Once had it with my bicycle, stopped on a hot day day driving home from work to see where the noice came from saw the inner tire blowing up trought a ripp in outer tire , and it blew, so had to walk home. Already saw earlyer crackes in outer tire, so damaged.


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