Max tire pressure increase when hot?

[wiredgeorge]

FYI: I don't have TPMS on my truck tires but do have it on my camper tires. They are LRE and inflated cold to 80 PSI prior to a trip. On a warm Texas day, pressure reading will go up to almost 90 PSI and that is to be expected. The max pressure to achieve full load rating is done when the tire is cold and whoever designs these things knows the tire will heat up when going down the road.

BTW: I bought a set of Cooper Discoverer A/T All-Season LT275/70R18 125S tires which are load range E for $745 which includes tax. There was a charge for mount/balance at the Walmart service department.

[hlh1]

Originally Posted by wiredgeorge

FYI: I don't have TPMS on my truck tires but do have it on my camper tires. They are LRE and inflated cold to 80 PSI prior to a trip. On a warm Texas day, pressure reading will go up to almost 90 PSI and that is to be expected. The max pressure to achieve full load rating is done when the tire is cold and whoever designs these things knows the tire will heat up when going down the road.

BTW: I bought a set of Cooper Discoverer A/T All-Season LT275/70R18 125S tires which are load range E for $745 which includes tax. There was a charge for mount/balance at the Walmart service department.

Good price on the Coopers!

[flybouy]

Originally Posted by hlh1

That's so correct, that I "don't know what I don't know". Where do I find scales? Do I just pull up to the truck scales that I see on the Interstates?

Some states don't apreciate non-commercial use of the scales. Take a look at Catscales.com They explain how to weigh trailers, costs, and locations. They also have a phone app that makes going into pay unnecessary. There are also other truck stops that have scales that may not be Cat scale brands. If you Google " truck scales near me" you should get results.

[wiredgeorge]

Originally Posted by hlh1

Good price on the Coopers!

I was surprised that my tires were hundreds less (apples to apples) than anywhere else. My Cooper tires were only a couple months old and made in Arkansas (not overseas). They ride quite a bit better than the cheapo tires I had previously (Americus Commercial - street tread).

[Tireman9]

Originally Posted by hlh1

What would be a max hot tire pressure percentage increase over the cold tire pressure? My tires max load is at 35 psi, would a 20% psi increase when hot be a max air pressure before they pop? Or 25% psi increase?
Or I could ask it this way; what would be the max hot psi that I should sustain with these tires?

Do not get tied up with the tire hot pressure.


If you are not overloading or speeding your tires, the hot pressure is of no concern.
Note: Load and pressure are directly related. More load requires more inflation. Lower inflation means lower load capacity.


If your "cold" inflation (not warmed up from driving or sunlight) is set properly (at least what is shown in the load inflation tables + 10%) you do not need to worry about the hot pressure as we tire engineers know the pressure increases and we test accordingly.


They are not "going to pop" unless you run them overloaded and /or underinflatues

[Todd 423]

I fill mine to the max cold psi (110). I use a tpms and have seen them up to 125psi. remember the max psi on the tire is cold, you should expect them to increase with heat.

[Todd727]

Originally Posted by hlh1

I should have researched more before posting. My tires show a max PSI of 51. So, I'll set the cold at 35 psi for max load and then not worry too much until they get towards 51 psi.



When last towing the tires got up to 43 psi in air temps of 97 degrees. My infrared temp reader showed the tires at 130 degrees. The Carlisle trailer tires went from 63 psi to 70 psi and only showed 120 degrees.

And this is the problem with someone having a TPMS and not understanding tire inflation or how tires work and flex. That 51 PSI is COLD. If you set them to 35 PSI cold for max load, you will overheat and damage your tires over their lifetime.

Set them to 51 psi and quit looking at the pressure when the tires are warmed up.

[hlh1]

Originally Posted by Todd727

And this is the problem with someone having a TPMS and not understanding tire inflation or how tires work and flex. That 51 PSI is COLD. If you set them to 35 PSI cold for max load, you will overheat and damage your tires over their lifetime.

Set them to 51 psi and quit looking at the pressure when the tires are warmed up.

This is what I need to know. thanks!

[hlh1]

Originally Posted by Tireman9

Do not get tied up with the tire hot pressure.


If you are not overloading or speeding your tires, the hot pressure is of no concern.
Note: Load and pressure are directly related. More load requires more inflation. Lower inflation means lower load capacity.


If your "cold" inflation (not warmed up from driving or sunlight) is set properly (at least what is shown in the load inflation tables + 10%) you do not need to worry about the hot pressure as we tire engineers know the pressure increases and we test accordingly.


They are not "going to pop" unless you run them overloaded and /or underinflatues

More good info. thanks!

[jadatis]

To give you an idea howmuch the pressure can rise, and can be normal, I selected 3 cold pressures with their degrF/psi

35psi/10,5F/psi
80psi/ 5,5F/psi
120psi/ 4F /psi
This is assumed cold filled at 70degrF, but can use it for other temps filled to acurate enaugh.

What is important to prefent structural damage to the tire material, is that it wont get above a critical temperature . I dont know that temperature but will be in the range of 285degrF/ 140degrC.
Its always better to keep the tire material cooler.

Now the temperature of air ( or whatever gascompound) in the tire is related to that of the tirematerial and the surounding air ( ambiënt temperature) , if no external factors like sunshine on tire, heat of the brakes tranported trough the rims , exaust pipe directing to tire, etc.
1.
I estimated by reactions , that when driving 50 to 55mph, at ambiënt temp of 70degrF, with pressure in tire with enaugh reserve, the air in tire becomes about 110 to 115 degrF.
2.When 100degrF outside, will be about 20 degr (no 30)hotter so about 130 to 135degrF.

Filled at 70 degrF
1. 35psi rises 4psi to 39psi 2. 6psi to 41psi= 17%
1. 80 psi rises 8psi to 88psi. 2. 12psi to 92psi= 15%
1. 120psi rises 11psi to 131psi. 2. 15psi to 135psi= 12.5%

3.
Now external factor.
Descending from the mountains , and using the brakes to often, temp in tire can rise to 100degrC=212 degrF.
Will take a brake, and do the rest another time.

4.
And using to the max speed at 100degrF ambiënt temp of air in tire 160 degrF.



Now for all 3 selected pressures in the begin, I give , calculated with the degrF/psi to what it rises in the 4 situations, will add 3 and 4 later, or you can do it yourselfes.

[flybouy]

jadatis, I think your English translator is struggling and your metric math converter has completely failed.

[Camp CA]

Originally Posted by hlh1

What would be a max hot tire pressure percentage increase over the cold tire pressure? My tires max load is at 35 psi, would a 20% psi increase when hot be a max air pressure before they pop? Or 25% psi increase? Or I could ask it this way; what would be the max hot psi that I should sustain with these tires?

This article indicates " a good estimate is for every 10° fluctuation in air temperature, vehicle tire pressure will adjust by about 1 psi." https://www.tirebuyer.com/education/...d-temperature? AND this article indicates: "For cold tires, a tire pressure of 32-35 PSI is recommended. A tire pressure between 4 and 6 PSI above the recommended tire pressure is ideal for warm tires." https://www.carshtuff.com/post/cold-...ire%20pressure.

Suggest installing a tire pressure monitoring system (TPMS) to confirm.

[jadatis]

Originally Posted by flybouy

jadatis, I think your English translator is struggling and your metric math converter has completely failed.

That first might be right, but my math is OK.

Now situation 3, descending mountains , temp in tire 212 degrF. So external factor.
Did it exact , but using the degrF/psi I gave is acurate enaugh.
At 70 degr F filled
35 psi , becomes 48 psi = 37% rising
80psi becomes 105psi= 31% rising.
120psi becomes 156 psi= 30% rising
Because speed is relatively low then , probably tire material stil wont get above its critical temperature.

Situation 4, ambiënt temp 100 degr F , and driving with pressure with enaugh reserve, at maximum speed of tire.
Temp in tire 160 degrF

35 psi 》 43.5 psi = 24% rising
80 psi》 96 psi= 20% rising.
120 psi》 143 psi = 19% rising.

Situation 1, 2 and 4 is taken into account by the tiremakers. Situation 3 is external factor, but then you know at that moment that it is a external factor, so dont worry.

In any case dont lower the pressure, if you do that more deflection of tire, so more heatproduction, so tire material gets hotter, and most likely above critical temperature.

Pressure can get much higher on a tire wich is not damaged by overheating once.
So dont worry about the pressure, tires have test standards that they must stand 2 times the reference-pressure ( 80psi for E-load for instance, must stand 160 psi if new and undamaged).
Only the temperature, wich the pressure rising represents, is something to worry about.

[flybouy]

Originally Posted by jadatis

That first might be right, but my math is OK.

Now situation 3, descending mountains , temp in tire 212 degrF. So external factor.
Did it exact , but using the degrF/psi I gave is acurate enaugh.
At 70 degr F filled
35 psi , becomes 48 psi = 37% rising
80psi becomes 105psi= 31% rising.
120psi becomes 156 psi= 30% rising
Because speed is relatively low then , probably tire material stil wont get above its critical temperature.

Situation 4, ambiënt temp 100 degr F , and driving with pressure with enaugh reserve, at maximum speed of tire.
Temp in tire 160 degrF

35 psi 》 43.5 psi = 24% rising
80 psi》 96 psi= 20% rising.
120 psi》 143 psi = 19% rising.

Situation 1, 2 and 4 is taken into account by the tiremakers. Situation 3 is external factor, but then you know at that moment that it is a external factor, so dont worry.

In any case dont lower the pressure, if you do that more deflection of tire, so more heatproduction, so tire material gets hotter, and most likely above critical temperature.

Pressure can get much higher on a tire wich is not damaged by overheating once.
So dont worry about the pressure, tires have test standards that they must stand 2 times the reference-pressure ( 80psi for E-load for instance, must stand 160 psi if new and undamaged).
Only the temperature, wich the pressure rising represents, is something to worry about.

212 Deg Fahrenheit? No, your math is not correct.

[jadatis]

I read in contact with a valve importer , Rema Tiptop, that temperature in tire can incidentially rise to 100 degrC, is 212 degrF.
Also read that in racingcartires temp in tire can get 90 degrC = 194 degrF .

So yes 212 degr F is no mistake.
Can give you teststandards for normal snapp in valves with max cold pressure of 4,5 bar/ 65psi or 4.75 bar/ 69psi depending on brand.

DIN 78030 >>> first -40 degrC /144h, after that 100grC/48 hour/ +4,2 bar extra

ETRTO ( Europe) >> first -40 grC/48h/+1,8 bar/ after that 100 grC / 48 h/ +5,75 bar.
In 1 minut build up to 14 bar and hold this for 2 minutes.

SAE ( USA) >>>>first -40 degr C /4 hours/+1,8 bar, after that 100 degrC/ 72 hour/+1,8 bar.
12,4 bar/ hold this for 2minutes .

[hlh1]

Wow! That's a high temp for a tire. I only saw 130 degrees F on my tire.

[flybouy]

I guess I haven't taken my trailer on a track at high speeds yet. Jeeze, let's at least try to keep this relevant to the application and stop trying to impress folks with numbers and stats that will only confuse them. No one here could care less about racing tires, euro standards, etc.

[hazmat456]

https://www.yournexttire.com/trailer...flation-chart/

[jadatis]

My answers are totally on topic, gives topicstarter idea of when and howmuch pressure may rise.

[flybouy]

Originally Posted by jadatis

My answers are totally on topic, gives topicstarter idea of when and howmuch pressure may rise.

On topic and relevant are two very different terms in the English language.