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RoadTrip2084 10-20-2021 01:18 PM

1 Attachment(s)
Quote:

Originally Posted by RoadTrip2084 (Post 5956727)
One thing I haven't found is a reference for exactly what temperature the tire manufacturers use for their "cold" tire temp?

If I set my tires cold (before driving for the day) based on the recommended pressures for my weights, that seems like it could be a lot different if it's 32f vs 75f outside. But nobody seems to claim a standard for what "cold" means.

Okay, after a bit of "DuckDuckGo"ing, I've found at least one authoritative reference for this. Source: "COLD WEATHER RECOMMENDATIONS FOR ALL CATERPILLAR MACHINES - Excerpted from Operation & Maintenance Manual (SEBU5898-11-01)" (Link)

It would appear that pressure adjustment is warranted if you travel from a warm to a cold or cold to a warm location, or if the temps at your location change drastically.

In my neck of the woods, in spring and fall the daily temp. range can vary 30degrees. Since too low pressure is the main concern I'd fill my tires cold at the lowest ambient temp. I expect to drive them in, so long as the resulting warm tire pressures didn't exceed the sidewall limits.

Note that the difference in recommended pressure between normal/standard ambient cold inflation temp. (64 to 70deg F) and the recommended pressure at 32F is only 6% or 5lbs in my case.

See below:

Quote:

Tire Inflation Information SMCS Code: 4203 SEBU5898-11

Tires that are inflated below the recommended pressure will have shortened life. A tire that is inflated to the correct pressure in a 18 to 21įC (64 to 70įF) warm shop area will have an incorrect tire pressure in freezing temperatures.
Use dry nitrogen gas to inflate the tires. Nitrogen gas is N2. Dry nitrogen is recommended in order to eliminate ice crystals. Ice crystals could hold the valve stem open in the tire.

The table shows the correct pressures for tires that are inflated in an area with a temperature
of 18 to 21įC (64 to 70įF). These pressures are adjusted for the environmental working temperature of the machine.

Tire inflation should be done in a heated area. The tire bead will seat better when the tire bead is warm. The initial tire pressure should be fifteen to twenty percent higher than the operating pressure in order to seat the tire bead against the rim. Deflate the tires to operating pressure before operating the machine. The contact surface of tires will become flat in cold weather when a machine is parked. To return the tire to a normal shape, move the machine gradually.

wolfe10 10-20-2021 01:36 PM

Quote:

Originally Posted by RoadTrip2084 (Post 5956845)
Since too low pressure is the main concern I'd fill my tires cold at the lowest ambient temp. I expect to drive them in


////


so long as the resulting warm tire pressures didn't exceed the sidewall limits.

See below:


Agree with the first half or your statement.


The second half not at all. The PSI on the sidewall is for cold (before driving), and has no relationship to PSI after driving. I promise that the tire engineers are familiar with the Ideal Gas Law and absolutely know what PSI change occurs with increased temperature.


I would be surprised if most tires do not exceed the side wall PSI if driven on hot days at highway speeds.

jadatis 10-20-2021 01:37 PM

Though its always needed to determine pressure with a reserve, for savety of tire ( so tire never overheats) the pressure-fluctuation by ambiŽnt temperature dont need care. If colder , the lower pressure gives more deflection , so more heatproduction a cycle, so at same speed, but also cooling down of tires rubber is better because of more temperature-differences between rubber and in and outside tire air. So rubber still not overheats.

Hotter outside the other way around.

So when 100degrF outside, you need higher cold pressure then when 40 degrF outside.

The advice pressure is determined for 70 degrF in tire so cold measured also ambiŽnt temp.
I made several lists for pressure/temperature relation, but became to complicated to use.
But now I made a simple list, wich is yust as complicated as is needed for the importance of the goal, so read simple.

In that list search the pressure you determined to be needed with a reserve, and read behind it the degrF/psi and remember that ( so for every axle , if different pressure, remember the degrF/psi).

Then on the road you can calculate by head the needed pressure for cold filling, or when reading tmps pressure while driving, you can calculate acurate enaugh the temperature of the gascompound in the tire.

Here it is:

33 psi/ 11 F/psi
34 psi/ 11 F/psi
35 psi/ 10,5 F/psi
36 psi/ 10,5 F/psi
37 psi/ 10 F/psi
39 psi/ 10 F/ps
40 psi/ 9,5 F/psi
42 psi/ 9,5 F/psi
43 psi/ 9 F/psi
45 psi/ 9 F/psi
46 psi/ 8,5 F/psi
49 psi/ 8,5 F/psi
50 psi/ 8 F/psi
53 psi/ 8 F/psi
54 psi/ 7,5 F/psi
58 psi/ 7,5 F/psi
59 psi/ 7 F/psi
63 psi/ 7 F/psi
64 psi/ 6,5 F/psi
70 psi/ 6,5 F/psi
71 psi/ 6 F/psi
77 psi/ 6 F/psi
78 psi/ 5,5 F/psi
86 psi/ 5,5 F/psi
87 psi/ 5 F/psi
96 psi/ 5 F/psi
97 psi/ 4,5 F/psi
109 psi/ 4,5 F/psi
110 psi/ 4 F/psi
126 psi/ 4 F/psi
127 psi/ 3,5 F/psi
148 psi/ 3,5 F/psi

Tireman9 10-20-2021 02:19 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?


Yes you should always inflate tires when they are at Ambient temperature and not warmed from running or being in direct sunlight.
Depending on the pressure increase due to driving on tires in NOT CORRECT.


In my blog I recommend that the "set pressure" be at least 10% above the minimum pressure needed to support the heaviest load measured on the heaviest loaded tire.

Tireman9 10-20-2021 02:24 PM

Quote:

Originally Posted by davidceder (Post 5956642)
I put about 7 pounds extra in my tires and never adjust unless things go wrong. I mean if a cold front comes through I would have to find a station to add air. That is a PIA. Then I would need to let air out when the cold front moves through. Repeat, repeat repeat. I do not carry a pump as I don't have the space, want the weight or hassle. I have read on this forum from very reputable involved folks that they fill their tires at the beginning of the camping season and that is it unless they run into some problems. I live at 5000 feet so this AM is was 44 degrees at home and 64 degrees in Phoenix where I am headed. I topped them off at home and that is all. Sometimes I do indeed get an high pressure alert on my TPMS but I just silence it. During really hot seasons in AZ I might up my High Pressure limit on my TPMS so the alarms stop. Just my way of doing things.

You guys that adjust your times all the time, do you do that same thing with your cars?


You do not need to adjust your tires daily if you have a cushion. Pressure only changes about 2% for each change in ambient temperature of 10F, so having your "set pressure" at +10% you are good for a change in ambient of 50F which normally does not happen every day.


TPMS High pressure warning can be at +25% as you should not see that much increase unless running heavy and fast.


You do not need to adjust car tire pressure as most have the placard pressure at about +30% based on actual tire loading while RVs are lucky if they are set to +2% based on measured load.

RoadTrip2084 10-20-2021 02:27 PM

Quote:

Originally Posted by wolfe10 (Post 5956868)
Agree with the first half or your statement.


The second half not at all. The PSI on the sidewall is for cold (before driving), and has no relationship to PSI after driving. I promise that the tire engineers are familiar with the Ideal Gas Law and absolutely know what PSI change occurs with increased temperature.


I would be surprised if most tires do not exceed the side wall PSI if driven on hot days at highway speeds.

Yeah, that makes sense. Sidewall rating is max cold pressure required to support the max weight the tire can handle, which is hopefully quite a bit higher than the actual weight anyone needs it to on their rig.

MN_Traveler 10-20-2021 02:29 PM

Quote:

Originally Posted by jadatis (Post 5956871)
Though its always needed to determine pressure with a reserve, for savety of tire ( so tire never overheats) the pressure-fluctuation by ambiŽnt temperature dont need care. If colder , the lower pressure gives more deflection , so more heatproduction a cycle, so at same speed, but also cooling down of tires rubber is better because of more temperature-differences between rubber and in and outside tire air. So rubber still not overheats.

Hotter outside the other way around.

So when 100degrF outside, you need higher cold pressure then when 40 degrF outside.

The advice pressure is determined for 70 degrF in tire so cold measured also ambiŽnt temp.
I made several lists for pressure/temperature relation, but became to complicated to use.
But now I made a simple list, wich is yust as complicated as is needed for the importance of the goal, so read simple.

In that list search the pressure you determined to be needed with a reserve, and read behind it the degrF/psi and remember that ( so for every axle , if different pressure, remember the degrF/psi).

Then on the road you can calculate by head the needed pressure for cold filling, or when reading tmps pressure while driving, you can calculate acurate enaugh the temperature of the gascompound in the tire.

Here it is:

33 psi/ 11 F/psi
34 psi/ 11 F/psi
35 psi/ 10,5 F/psi
36 psi/ 10,5 F/psi
37 psi/ 10 F/psi
39 psi/ 10 F/ps
40 psi/ 9,5 F/psi
42 psi/ 9,5 F/psi
43 psi/ 9 F/psi
45 psi/ 9 F/psi
46 psi/ 8,5 F/psi
49 psi/ 8,5 F/psi
50 psi/ 8 F/psi
53 psi/ 8 F/psi
54 psi/ 7,5 F/psi
58 psi/ 7,5 F/psi
59 psi/ 7 F/psi
63 psi/ 7 F/psi
64 psi/ 6,5 F/psi
70 psi/ 6,5 F/psi
71 psi/ 6 F/psi
77 psi/ 6 F/psi
78 psi/ 5,5 F/psi
86 psi/ 5,5 F/psi
87 psi/ 5 F/psi
96 psi/ 5 F/psi
97 psi/ 4,5 F/psi
109 psi/ 4,5 F/psi
110 psi/ 4 F/psi
126 psi/ 4 F/psi
127 psi/ 3,5 F/psi
148 psi/ 3,5 F/psi

I was iniitally going to react badly to this advise .... but after reading your post (several times) I think I just to not really understand at all what you are trying to say. Can you please try re-phasing to clarify? (the advise that you need a different cold tire inflation based on what the ambient pressure is runs counter to everything that is written and taught .... but again, I suspect there is something here that is not coming across clearly.....)

MN_Traveler 10-20-2021 02:34 PM

Quote:

Originally Posted by RVStitchy (Post 5956810)
To better understand the logic I have a question. Is the difference between cold and hot (ordinary highway running) temps always the same delta? Or will tires come up to the same hot temp regardless of the starting cold temps?

I have lived in South Florida for the last 50 years so not much experience with your frigid sub 40 temps.

I plan on recording this data with TPMS in the future but have no plans to be anywhere this year that is below 50F to experiment.

The tires do NOT always come up to the same operating temperature with different outside temperatures. Generally speaking (but it is more complicated than this), the tires will see the same temperature change, increasing from their starting temperature.

So, if they generally see, say (just an example), a ten degree rise, if they start at 30 degrees, they will settle out at 40 degrees. But if they start at 100 degrees, they will settle out at about 110 degrees. another way of seeing this is that the pressure rise from starting pressure will be about the same, regardless of the temperature the tires started at. again, this is a general statement, and other things (like variations in load, direction of sun hitting tires, side winds, etc) will make for some degree of variation from the above statement.

Tireman9 10-20-2021 02:36 PM

Quote:

Originally Posted by RVStitchy (Post 5956810)
To better understand the logic I have a question. Is the difference between cold and hot (ordinary highway running) temps always the same delta? Or will tires come up to the same hot temp regardless of the starting cold temps?

I have lived in South Florida for the last 50 years so not much experience with your frigid sub 40 temps.

I plan on recording this data with TPMS in the future but have no plans to be anywhere this year that is below 50F to experiment.




Running pressure with no change in Ambient will usually be between +10% and + 20% which assumed the tires are not overloaded and you are not running faster than about 60 MPH AND that you set the "cold" pressure based on actual tire load and used the minimum inflation in the tables + 5% to +10%.


Run faster or heavier or not setting the initial pressure correctly will of course affect these numbers.

MN_Traveler 10-20-2021 02:39 PM

Quote:

Originally Posted by Fiesta48 (Post 5956829)
Way over kill posted here. Check all tires in the spring and fall. And just before each trip. 5 psi difference due to temps won't hurt any tire.
Low pressure will. Doing this for 60+ years.

Not so sure about the basic premise here. I once drove, in one day, from southern MO to minneapolis. When I left MO it was above freezing. When I hit minnesota, the ambient temperature was sub zero. Tire cold pressures were fine when I left MO. When I hit minnesota, the tire pressures were pushing their minimum inflation limit for load, while I was running at highway speed. so their equivalent "cold" pressure (say if I had stopped to rest for half an hour) would have been below the minimum cold inflation.

I never move my rig more than ten feet unless I know my tires are above minimum pressure.

Tireman9 10-20-2021 02:40 PM

Quote:

Originally Posted by wolfe10 (Post 5956868)
Agree with the first half or your statement.


The second half not at all. The PSI on the sidewall is for cold (before driving), and has no relationship to PSI after driving. I promise that the tire engineers are familiar with the Ideal Gas Law and absolutely know what PSI change occurs with increased temperature.


I would be surprised if most tires do not exceed the side wall PSI if driven on hot days at highway speeds.


Brett is 100% correct. I know as I am an actual tire design engineer.

Tireman9 10-20-2021 02:44 PM

Quote:

Originally Posted by RoadTrip2084 (Post 5956845)
Okay, after a bit of "DuckDuckGo"ing, I've found at least one authoritative reference for this. Source: "COLD WEATHER RECOMMENDATIONS FOR ALL CATERPILLAR MACHINES - Excerpted from Operation & Maintenance Manual (SEBU5898-11-01)" (Link)

It would appear that pressure adjustment is warranted if you travel from a warm to a cold or cold to a warm location, or if the temps at your location change drastically.

In my neck of the woods, in spring and fall the daily temp. range can vary 30degrees. Since too low pressure is the main concern I'd fill my tires cold at the lowest ambient temp. I expect to drive them in, so long as the resulting warm tire pressures didn't exceed the sidewall limits.

Note that the difference in recommended pressure between normal/standard ambient cold inflation temp. (64 to 70deg F) and the recommended pressure at 32F is only 6% or 5lbs in my case.

See below:




Way to involved unless you are in Alaska in the winter and inflating tires when they are warmed indoors. That is not Ambient (Air temperature in the shade) There are similar charts for the military.


I think this forum is more concerned for normal highway service in the "lower 48 at temperatures from 0F to 100F AMBIENT.


Note a change of ambient of 100 degrees will only result in about a 20% change in tire inflation pressure. That's the reality of the "Gas Law"

Tireman9 10-20-2021 02:45 PM

Quote:

Originally Posted by jadatis (Post 5956871)
Though its always needed to determine pressure with a reserve, for savety of tire ( so tire never overheats) the pressure-fluctuation by ambiŽnt temperature dont need care. If colder , the lower pressure gives more deflection , so more heatproduction a cycle, so at same speed, but also cooling down of tires rubber is better because of more temperature-differences between rubber and in and outside tire air. So rubber still not overheats.

Hotter outside the other way around.

So when 100degrF outside, you need higher cold pressure then when 40 degrF outside.

The advice pressure is determined for 70 degrF in tire so cold measured also ambiŽnt temp.
I made several lists for pressure/temperature relation, but became to complicated to use.
But now I made a simple list, wich is yust as complicated as is needed for the importance of the goal, so read simple.

In that list search the pressure you determined to be needed with a reserve, and read behind it the degrF/psi and remember that ( so for every axle , if different pressure, remember the degrF/psi).

Then on the road you can calculate by head the needed pressure for cold filling, or when reading tmps pressure while driving, you can calculate acurate enaugh the temperature of the gascompound in the tire.

Here it is:

33 psi/ 11 F/psi
34 psi/ 11 F/psi
35 psi/ 10,5 F/psi
36 psi/ 10,5 F/psi
37 psi/ 10 F/psi
39 psi/ 10 F/ps
40 psi/ 9,5 F/psi
42 psi/ 9,5 F/psi
43 psi/ 9 F/psi
45 psi/ 9 F/psi
46 psi/ 8,5 F/psi
49 psi/ 8,5 F/psi
50 psi/ 8 F/psi
53 psi/ 8 F/psi
54 psi/ 7,5 F/psi
58 psi/ 7,5 F/psi
59 psi/ 7 F/psi
63 psi/ 7 F/psi
64 psi/ 6,5 F/psi
70 psi/ 6,5 F/psi
71 psi/ 6 F/psi
77 psi/ 6 F/psi
78 psi/ 5,5 F/psi
86 psi/ 5,5 F/psi
87 psi/ 5 F/psi
96 psi/ 5 F/psi
97 psi/ 4,5 F/psi
109 psi/ 4,5 F/psi
110 psi/ 4 F/psi
126 psi/ 4 F/psi
127 psi/ 3,5 F/psi
148 psi/ 3,5 F/psi




Nope. Too involved.

Tireman9 10-20-2021 02:49 PM

Quote:

Originally Posted by MN_Traveler (Post 5956942)
I was iniitally going to react badly to this advise .... but after reading your post (several times) I think I just to not really understand at all what you are trying to say. Can you please try re-phasing to clarify? (the advise that you need a different cold tire inflation based on what the ambient pressure is runs counter to everything that is written and taught .... but again, I suspect there is something here that is not coming across clearly.....)


jadats is Dutch so English is not his first language. He tries hard and does a better job than I would if I had to post in Dutch. Sometimes i think he tries too hard and we end up over complicated.


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