Tire Pressure

[ricky5924]

I have the EEZE tire TPMS. I've noticed that when I get in the RV to go camping, I start out with the pressure I run in all the tires, 80-82 psi at a temperature say around 75°F. After i drive for an hour or so the pressure will rise to about 95-98 psi and the temperature will rise to around 100°F. I know the EEZE tire is giving a good reading on the pressure, I've checked them hot and cold with a manual and digital tire gauge. I know they are going to heat up and build pressure, just seems like a lot of difference in psi and temperature. Is this normal? Thoughts? 19.5" tire.

[EA37TS]

Originally Posted by ricky5924

I have the EEZE tire TPMS. I've noticed that when I get in the RV to go camping, I start out with the pressure I run in all the tires, 80-82 psi at a temperature say around 75°F. After i drive for an hour or so the pressure will rise to about 95-98 psi and the temperature will rise to around 100°F. I know the EEZE tire is giving a good reading on the pressure, I've checked them hot and cold with a manual and digital tire gauge. I know they are going to heat up and build pressure, just seems like a lot of difference in psi and temperature. Is this normal? Thoughts? 19.5" tire.

Normal.

[ricky5924]

Originally Posted by EA37TS

Normal.

[Pete'sMH]

Normal and I’ve even seen bigger increases after a long highway run on a hot day.

[ricky5924]

Originally Posted by Pete'sMH

Normal and I’ve even seen bigger increases after a long highway run on a hot day.

Thanks

[Lt Keefer]

I use a point and shoot thermometer to check the tire temps during my rest stops. I have seen 125 degrees after a couple of hours on the interstate going across Texas.

[Beau388]

Originally Posted by ricky5924

I have the EEZE tire TPMS. I've noticed that when I get in the RV to go camping, I start out with the pressure I run in all the tires, 80-82 psi at a temperature say around 75°F. After i drive for an hour or so the pressure will rise to about 95-98 psi and the temperature will rise to around 100°F. I know the EEZE tire is giving a good reading on the pressure, I've checked them hot and cold with a manual and digital tire gauge. I know they are going to heat up and build pressure, just seems like a lot of difference in psi and temperature. Is this normal? Thoughts? 19.5" tire.

This has been discussed many times on this Forum. It is the air in the tires that hold up the coach not the tire its self. The tire is simply an air bladder. Air expands when heated water vapor expands note than air when heated. It is known as Gay-Lussac's pressure temperature law. Using the ideal gas it becomes PV= nRT. If the volume is fixed the equations comes 0= kT/P or P=kT. So pressure is directly proportional to temperature. We will the units out of the equation.
When the tire flexes (remember is is flat on the bottom) it heats up and transfers the heat to the air around it, including that inside the tire. The more the weight on the tire the more heat, the faster you drive the more heat, the sharper the curves the more the heat and the rougher the road the more the tire heats up. So there is no normal, average or acceptable chart as to what the temperature/pressure gain. For me in with a 18,000 lb coach, running 60 mph on asphalt on a 100 F degree day, there is a 24 degree rise when starting at 80 F degree morning at 88 psi. It is true the the inside dual tires heat up more than the outside. This is due to the lack of cool air flowing across the tires. The reason there is a speed limit on most tires is if the tires exceed that speed of a considerable time at rated pressure the tire can overheat and the rubber de-laminate.

It is nice to live beside a chemical engineer who formulated the rubber used in Hoosier racing tires for 30+ years.

[Chateau_Nomad]

BAM!

I'm preparing to purchase a TPMS for the toad... now I know what to expect!

[lwmcguire]

Originally Posted by Beau388

This has been discussed many times on this Forum. It is the air in the tires that hold up the coach not the tire its self. The tire is simply an air bladder. Air expands when heated water vapor expands note than air when heated. It is known as Gay-Lussac's pressure temperature law. Using the ideal gas it becomes PV= nRT. If the volume is fixed the equations comes 0= kT/P or P=kT. So pressure is directly proportional to temperature. We will the units out of the equation.
When the tire flexes (remember is is flat on the bottom) it heats up and transfers the heat to the air around it, including that inside the tire. The more the weight on the tire the more heat, the faster you drive the more heat, the sharper the curves the more the heat and the rougher the road the more the tire heats up. So there is no normal, average or acceptable chart as to what the temperature/pressure gain. For me in with a 18,000 lb coach, running 60 mph on asphalt on a 100 F degree day, there is a 24 degree rise when starting at 80 F degree morning at 88 psi. It is true the the inside dual tires heat up more than the outside. This is due to the lack of cool air flowing across the tires. The reason there is a speed limit on most tires is if the tires exceed that speed of a considerable time at rated pressure the tire can overheat and the rubber de-laminate.

It is nice to live beside a chemical engineer who formulated the rubber used in Hoosier racing tires for 30+ years.

Good info from Beau

I use temperature and have for the past 60 plus years as the easy indicator of what is going on

Given you have to account for direct sunlight as a huge factor

However if you have tires with the same load and one is indicating a much higher temperature check the pressure and load of the axle

corner weights are the best way and then you inflate the tires on that axle to the value required for the heaviest actual weight

If you have to travel on a very hot day on hot asphalt it isn't the day to be pushing the speed as it adds even more heat that has a hard time disipating

[ricky5924]

Originally Posted by Beau388

This has been discussed many times on this Forum. It is the air in the tires that hold up the coach not the tire its self. The tire is simply an air bladder. Air expands when heated water vapor expands note than air when heated. It is known as Gay-Lussac's pressure temperature law. Using the ideal gas it becomes PV= nRT. If the volume is fixed the equations comes 0= kT/P or P=kT. So pressure is directly proportional to temperature. We will the units out of the equation.
When the tire flexes (remember is is flat on the bottom) it heats up and transfers the heat to the air around it, including that inside the tire. The more the weight on the tire the more heat, the faster you drive the more heat, the sharper the curves the more the heat and the rougher the road the more the tire heats up. So there is no normal, average or acceptable chart as to what the temperature/pressure gain. For me in with a 18,000 lb coach, running 60 mph on asphalt on a 100 F degree day, there is a 24 degree rise when starting at 80 F degree morning at 88 psi. It is true the the inside dual tires heat up more than the outside. This is due to the lack of cool air flowing across the tires. The reason there is a speed limit on most tires is if the tires exceed that speed of a considerable time at rated pressure the tire can overheat and the rubber de-laminate.

It is nice to live beside a chemical engineer who formulated the rubber used in Hoosier racing tires for 30+ years.

Thank You, I think

[Wiley1]

Originally Posted by Beau388

It is known as Gay-Lussac's pressure temperature law. Using the ideal gas it becomes PV= nRT. If the volume is fixed the equations comes 0= kT/P or P=kT. So pressure is directly proportional to temperature.
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I'm pretty sure I know these answers, but I'll ask anyway.

Is there any difference in the performance of the tires when using 100% nitrogen instead of 78% nitrogen?
Will there be any difference in the longevity of the tires because of dry rot and other factors?

[jadatis]

Originally Posted by ricky5924

I have the EEZE tire TPMS. I've noticed that when I get in the RV to go camping, I start out with the pressure I run in all the tires, 80-82 psi at a temperature say around 75°F. After i drive for an hour or so the pressure will rise to about 95-98 psi and the temperature will rise to around 100°F. I know the EEZE tire is giving a good reading on the pressure, I've checked them hot and cold with a manual and digital tire gauge. I know they are going to heat up and build pressure, just seems like a lot of difference in psi and temperature. Is this normal? Thoughts? 19.5" tire.

Even if I fill in 82 psi at 70 degr F , and it goes to 95psi, then temp in tire is 141 degr F.
So your tmps gives pretty exact,( as you tested) the temperature at the end of the valve, and not of the gascompound in the tire.

I once estimated that if you drive about 55mph at ambiënt temp of 65 degrF with high enaugh pressure for load and 99mph, temp in tire rises to 115 degrF, and with that pressure rises about 10%.

Goal of pressure advice is that the rubber of tire wont reach a critical temp at wich it hardens and beginning cracks are made. This is allowed to happen ZERO times in a tires live.

If no external factors, the tire inside temp is related to that of the rubber of tire, and max inside tire at ambiënt temp of 65 degrF, is allowed to reach about 140 degrF.

So if you did not have those external factors, like sunshine on tires, severe braking or hot ambiënt temp or roadsurface, the 141 degrF in best case scenario yust wont overheat the rubber.

But worst case scenario , so 80 psi at 75 degrF, goes to 98 psi, gives 177 degrF, and that must be to hot without external factors.

Then its wise to review the cold pressure-advice, it will need higher cold pressure to produce lesser heat, so temp of rubber stays colder, and with that lower temp in tire, so less % pressure rising, but warm pressure will even be higher.
No problem that high pressure, tire is designed for that, the temperature of rubber of tire is what its all done for.

[jadatis]

Made you a list for the pressure/temp relation for 80psi filled or measured at 70 degrF.
Assumes no vollume change, wich it will practically be for an already presurised tire.
Been experimenting with a 10% volume rising from zero to referencepressure of tire( yours probably 80 psi) and it gave more temperature change per psi, so wont work that out further, because even at the pressure that gave 212 degrF( boiling temp of water) only 12 degr F higher temp.

You can print it out and glu it on dasboard to give beter inside tire temp indication then your external tmps sensors.
F. / PSI
14 / 70
25 / 72
36 / 74
48 / 76
59 / 78
70 / 80 advice-pressure
81 / 82
92 / 84
104 / 86
115 / 88
126 / 90
137 / 92
148 / 94
160 / 96
171 / 98
182 / 100
193 / 102
204 / 104
215 / 106
227 / 108
F. / PSI

[Wiley1]

This is really interesting stuff.

but, does it have any practical use?

[16ACE27]

Originally Posted by Wiley1

I'm pretty sure I know these answers, but I'll ask anyway.

Is there any difference in the performance of the tires when using 100% nitrogen instead of 78% nitrogen?
Will there be any difference in the longevity of the tires because of dry rot and other factors?

Hopefully your known answer is "no, no difference except lighter wallet."

[Rick T]

Originally Posted by Wiley1

I'm pretty sure I know these answers, but I'll ask anyway.

Is there any difference in the performance of the tires when using 100% nitrogen instead of 78% nitrogen?
Will there be any difference in the longevity of the tires because of dry rot and other factors?

Nitrogen is a stable gas - does not expand as much as "normal air" with increased temperature. I have nitrogen in my car tires - the pressure does not vary much at all from summer to winter. Only problem is if you do need to add air then you start to have pressure variances.

[jadatis]

Dont know how you determined that, but Nitrogen expands and schrinks exactly the same as any other gas. Only the lack of water in nitrogen tanks can make a difference, and then even marginal in cold pressure.
Once downloaded a water spreadsheet wich gave max partial pressure of watergas for temperature, and added psi and degrF colom to it.
Then at 65 degrF max 0.3psi water as gas, and at 140degrF max 2.9psi water as gas , so then if gascompound without water in tire , topicstarters 82 psi would rise to 95 psi with dry air, and 2.6 psi more if enaugh liqiud water in tire to go over to gas. Yudge for yourselves if that is worth filling with nitrogen.
But same effect can be reached by filling with dry air.

If you fill with Compressor with tank , then first give the tank an as high possible pressure, so water condenses an tap of the water, then the air in the tank( or is it vessel) is dry enaugh.
Even if you dont drain the vessel, the liquid water at the bottom wont get into the tube .

But again , not worth the trouble for that 2.6 psi difference. Gives lesser deflection so heatproduction, so rubber stays a bit colder, so water in tire even better then dry gascompound.

[jadatis]

Originally Posted by Wiley1

This is really interesting stuff.

but, does it have any practical use?

If you answer this to me, same practical use as temperature reading of tmps, to my opinion not much.

But to understand what is important for tire its usefull.

[Jimbo56]

Originally Posted by Chateau_Nomad

BAM!

I'm preparing to purchase a TPMS for the toad... now I know what to expect!

Great idea for peace of mind. I put sensors on my trailer tires.

[Jimbo56]

Nitrogen is a way for a tire dealer to increase their bottom line. Might make a difference if you race for a living.