"Cold" tire pressure.

[Sequoiasoon]

guy bought 2018 mitsubishi asx, has tpms, but can´t see any numbers... pretty stupid system imho

My 2017 Accord doesn't have any TPMS sensors. It uses wheel speed through ABS.
My brother-in-law has a VW Tiguan I think '16 or '17 same thing, no TPMS sensors, ABS based.

Nice feature is no reprogramming needed when you switch to winter rims/tires. Check pressures, push calibrate button and drive.

My son's 2010 Forte has TPMS sensors that need program but also no readouts, needed second set for winter rims/tires programmed. Set pressures on a hot day. 3 days later it was almost 70 degrees colder. low pressure turned on. Checked and all were about 5 psi low.

My daughters '08 CRV has TPMS sensors, no readouts, needed second set of sensors for winter. Didn't know I could order "cloned" sensors. CRV only holds 4 sensors in ECU. Needs TPMS programming tool each season wheel swap. If not done TPMS "system" problem illuminates and makes it so you can not shut off the ESC/VSC so if stuck in snow/mud you can't spin the wheels as it totally limits wheel spin.

Accord - ABS system. I had the wheels rebalanced and they inflated to 35 all around. I normally run 34 front/33 rear. My tire pressure/TPMS went on about 2 miles down the road. The overinflation from where it was calibrated triggered it. I let some air out respectively and it went away.

'19 Pilot and '16 Renegade have the readouts. It is nice to be able to see what the pressure is while driving but the "stupid" no display systems work just fine and often less headaches and hassles.

 

[hrv]

My 2017 Accord doesn't have any TPMS sensors. It uses wheel speed through ABS.
My brother-in-law has a VW Tiguan I think '16 or '17 same thing, no TPMS sensors, ABS based.

Nice feature is no reprogramming needed when you switch to winter rims/tires. Check pressures, push calibrate button and drive.

My son's 2010 Forte has TPMS sensors that need program but also no readouts, needed second set for winter rims/tires programmed. Set pressures on a hot day. 3 days later it was almost 70 degrees colder. low pressure turned on. Checked and all were about 5 psi low.

My daughters '08 CRV has TPMS sensors, no readouts, needed second set of sensors for winter. Didn't know I could order "cloned" sensors. CRV only holds 4 sensors in ECU. Needs TPMS programming tool each season wheel swap. If not done TPMS "system" problem illuminates and makes it so you can not shut off the ESC/VSC so if stuck in snow/mud you can't spin the wheels as it totally limits wheel spin.

Accord - ABS system. I had the wheels rebalanced and they inflated to 35 all around. I normally run 34 front/33 rear. My tire pressure/TPMS went on about 2 miles down the road. The overinflation from where it was calibrated triggered it. I let some air out respectively and it went away.

'19 Pilot and '16 Renegade have the readouts. It is nice to be able to see what the pressure is while driving but the "stupid" no display systems work just fine and often less headaches and hassles.

My 2021 Honda HRV had this system and I love it....Also you have the traditional rubber valve stem....

 

[ARCOgraphite]

I got extra set of green caps in Wal Mart. I am all set

I used to use a outdoor timed pay-for pump at a local Sunoco station. Then in the fall when airing up I noticed tons of water coming out of the hose. when i was clearing sand out of the head. I said to myself this isnt good, and I imagine if you have tpms it would be even worse with some designs. So dry bottled nitrogen is a way to keep water out. The other more traditional way is having a good lubricator /dryer on that big shop compressor - and bleeding the tank bottom weekly.

 

[edyvw]

I used to use a outdoor timed pay-for pump at a local Sunoco station. Then in the fall when airing up I noticed tons of water coming out of the hose. when i was clearing sand out of the head. I said to myself this isnt good, and I imagine if you have tpms it would be even worse with some designs. So dry bottled nitrogen is a way to keep water out. The other more traditional way is having a good lubricator /dryer on that big shop compressor - and bleeding the tank bottom weekly.

I do it in my garage with small electrical compressor. Usually in the morning when tires are cold.
I have seen before those gas station compressors blowing liquid or dirt. Unless emergency, I avoid it.

 

[George Bynum]

Now the bit about changes in pressure due to ambient temperature. The rule of thumb for passenger car tires is 1 psi for every 10°F. For truck and trailer tires that rule is 2% for every 10°F.

I'd like to know what saying truck or trailer has to do with the ideal gas law? Using absolute units for pressure and temperature, P1*V1*T2=P2*V2*T1, right? So does the volume of a truck/trailer tire decrease approximately linearly with temperature?

 

[eljefino]

Water vapor has way more temperature/ pressure variability than dry air. The nitrogen machine also dries air nicely.

I try like heck to change the air in my tires when a real cold snap rolls through, to get low absolute humidity in there. I feel it benefits internal rim corrosion. Haven't seen if it makes my pressures more consistent. Just something I do as a "best practice" without, of course, paying for Nitrogen. Concerned I might have frost/ ice inside so I do it after a drive that warms the tires up.

 

[Oily_Thing]

Front brakes can definitely heat up the front tires too.

 

[jadatis]

I'd like to know what saying truck or trailer has to do with the ideal gas law? Using absolute units for pressure and temperature, P1*V1*T2=P2*V2*T1, right? So does the volume of a truck/trailer tire decrease approximately linearly with temperature?

(Yeah, I'm being a (un)smart a$$). But enquiring minds want to know.

Read back my post #23 for that. And I will search for my post elswere in wich I explaine why its different for low pressures then high( used for trucktires). Has to do with the difference between gaugepressure and absolute pressure, wich are closer together at high filled pressure, then at low filled pressure.
See post#29 in this RV topic. https://www.airforums.com/forums/f4...nd-pressure-results-230345-2.html#post2565449

 

[CapriRacer]

Water vapor has way more temperature/ pressure variability than dry air. The nitrogen machine also dries air nicely.

No, it doesn't. Water vapor - aka steam - behaves according to the ideal gas law, just like all gases do! (at least within the temperatures and pressure encountered by humans.)

Where the problem comes in is if you have saturated air - that is 100% humidity. Then when the temperature is reduced, water vapor condenses - aka as dew or rain, - and that affects the pressure.

- BUT -

When you fill a tire with air, you fill it from a higher pressure source - where the water has been condensed out. So the air in the tire is at LESS than 100% humidity.

Further, the water vapor is at a higher partial pressure than the outside air, so the water vapor permeates through the ever so slightly porous rubber, eventually reaching an equilibrium with the outside air - BUT - at a humidity level where the condensation temperature is really low. That's why you rarely see water inside a tire.

In other words: The only time water vapor is a problem is shortly after the tire is mounted. And for street usage, that hardly matters even in cold weather.

 

[CapriRacer]

I'd like to know what saying truck or trailer has to do with the ideal gas law? Using absolute units for pressure and temperature, P1*V1*T2=P2*V2*T1, right? So does the volume of a truck/trailer tire decrease approximately linearly with temperature?

It isn't the volume, it's the pressure.

Yes, even the air in truck and trailer tires behaves according to the ideal gas law. For passenger car tires, the rule of thumb is 1 psi for every 10°F, but when higher pressures are used, - like in truck or trailer tires (50 to 80 psi) - the value is higher - and 2% is close enough (just like 1 psi is close enough for 35 psi passenger car tires!) It's not exact, but I don't want people thinking the passenger car tire rule can be used for the higher pressures found in truck and trailer tires.

Now, do we need to talk about 100 psi bicycle tires? Or how about airplane tires where some are inflated to 400 psi!

 

[jadatis]

OK then , I will give a list of howmuch the pressure can maximally highen up or lower down extra if enaugh liquid water in the tire.
Assumed recomended pressure filled at 68 degrF , and water as gas 100% humidity . Then i substracted what the partial pressure of watergas rises or lowers the same as any other gas by temperature, from the maximum partial pressure of water belonging to the temperature, and this then is what the tirepressure extra rises with water in tire against perfectly dry gascompound ( air or more nitrogen ) . This is for low pressure the same extra as for high pressure in tire, so can be important for racecars, but for RV tires marginal, certainly in colder temperatures
Then that part is covered, now busy with howmuch of the other gasses disolve in the eventual liquid water in tire
At high pressure in tire more disolves, and at low temperature also more dissolves.
In the end this can extra rise or lower the pressure when liquid water in tire extra.
But think effect will prove even less then what I described first in common use of tires.

Example 36psi filled at 100degrF, and after that temp in tire drps to 15 degrF.
Pressure when perfect dry gascompound in tire drops to 28.3 degrF.
Extra by water in tire 100/0.602psi goes to 15degrF/ -0.265psi, so extra dropp by water 0.602- -0.265psi= 0.867psi lower so 28.3- 0.867= 27.43psi.
So even in this case a substantial extra dropp assuming no gasses dissolve in the liquid water, against my expectation, I have to admit.


15 F./ -0,265 psi
20 F./ -0,257 psi
25 F./ -0,248 psi
30 F./ -0,233 psi
35 F./ -0,219 psi
40 F./ -0,199 psi
45 F./ -0,179 psi
50 F./ -0,150 psi
55 F./ -0,114 psi
60 F./ -0,079 psi
64 F./ -0,038 psi
68 F./ 0,000 psi
70 F./ 0,020 psi
75 F./ 0,089 psi
80 F./ 0,156 psi
85 F./ 0,249 psi
90 F./ 0,337 psi
95 F./ 0,460 psi
100 F./ 0,602 psi
105 F./ 0,738 psi
110 F./ 0,922 psi
115 F./ 1,095 psi
120 F./ 1,331 psi
125 F./ 1,548 psi
130 F./ 1,854 psi
135 F./ 2,132 psi
140 F./ 2,507 psi
145 F./ 2,929 psi
150 F./ 3,317 psi
155 F./ 3,844 psi
160 F./ 4,324 psi
165 F./ 4,964 psi
170 F./ 5,552 psi
175 F./ 6,329 psi
180 F./ 7,038 psi
185 F./ 7,974 psi
190 F./ 9,006 psi
194 F./ 9,752 psi
198 F./ 10,548 psi
201 F./ 11,394 psi
205 F./ 12,294 psi

208 F./ 13,251 psi
210 F./ 13,752 psi
212 F./ 14,268 psi

 

[hrv]

Way overthinking this simple thing to do............

 

[kschachn]

guy bought 2018 mitsubishi asx, has tpms, but can´t see any numbers... pretty stupid system imho.

I very much prefer the indirect ones such as on my Tiguan. No worries when it comes to installing winter tires and any other time they are changed for that matter. I can measure the pressure with a gauge when I want.

 

[4WD]

I very much prefer the indirect ones such as on my Tiguan. No worries when it comes to installing winter tires and any other time changed for that matter. I can measure the pressure with a gauge when I want.

I spend half my life overseas and have warned my wife several times she needs to get a tire checked. I ask if the dash shows what my email shows - Yes … but thinking the winter pressure changes just go on year round in her mind …

 

[Badgerstate]

How many miles/minutes of driving are needed before a tire is no longer considered to be at "cold" temperature. I feel like this is never actually discussed when you buy a new set of tires with respect to longevity. Also if you are just idling down the road, does a tire ever really reach a "normal operating" pressure? How about ambient temperature? Seems like the tire industry deliberately leave this undefined to further their own interests....

Id say that once you drive a mile, its not longer cold. I know that when I was in high school and took drivers ed (back in the '90s), one of the teachers told us that you always wanted to set the cold psi when the vehicle has sat overnight.

 

[Rmay635703]

Sorry, what's the correlation ?

Identical Tires, Identical cars, identical miles, identical rotations

 

[OVERKILL]

Identical Tires, Identical cars, identical miles, identical rotations

View attachment 93037

When I say nothing bad is going to happen if you set the pressures too high, I'm talking about 10% or so high. I'm also saying that nothing terrible is going to happen to the traction, handling or wear. Just as an example, tire wear is more affected by alignment than it is inflation pressure. Even driving style has more affect on tire wear than inflation pressure does.

 

[krzyss]

Identical alignment? Identical roads travelled?

Krzys

 

[ARB1977]

When it’s hot out I check them first thing in the morning. When it’s cold out before the first drive.

 

[Oily_Thing]

I had a Lincoln Navigator with nitrogen filled tires. Total waste of money! Pressure dropped in winter and rose in the summer.

Nitrogen in tires is just a marketing gimmick.