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Topic: Tire pressure increase cold vs hot, nitrogen vs air (Read 922 times) previous topic - next topic

Tire pressure increase cold vs hot, nitrogen vs air

Has anyone conducted such a test?  I know my rig has air in the tires now, and I see ~16-18psi increase from cold to hot on the fronts, ~ 10-12psi on the drives and ~10 on the tags.  I'm wondering if going to nitrogen would have less of a pressure increase and if so, any guesses as to how much?
Keith
2003 U320 38' #6197

Re: Tire pressure increase cold vs hot, nitrogen vs air

Reply #1 –
Yes it does help but I've never worried about it. We use 100% nitrogen at work and I only use 78% at home. Good enough for me.
https://www.tirerack.com/tires/tiretech/techpage.jsp?gclid=Cj0KCQiAiJSeBhCCARIsAHnAzT-n150LEjM8zlc6TkB67Up88iLuJSsfnVTwohadME1T4K1ndBbvceoaAkYBEALw_wcB&techid=191&ef_id=Cj0KCQiAiJSeBhCCARIsAHnAzT-n150LEjM8zlc6TkB67Up88iLuJSsfnVTwohadME1T4K1ndBbvceoaAkYBEALw_wcB:G:s&s_kwcid=AL!3756!3!354820920608!e!!g!!air%20vs%20nitrogen&gclsrc=aw.ds
Quote;
Overall, inflating tires with nitrogen won't hurt them and may provide some minimal benefits.

Is it worth it? If you go someplace that provides free nitrogen with new tires, why not? Additionally we've seen some service providers offering reasonable prices of about $5 per tire (including periodic adjustments for the life of the tire) to a less reasonable $10 per tire (with additional costs for subsequent pressure adjustments) or more as part of a service contract, which we believe exceeds the value of nitrogen's benefit.

Rather than pay extra for nitrogen, most drivers would be better off buying an accurate tire pressure gauge and checking and adjusting their tire pressures regularly.

Re: Tire pressure increase cold vs hot, nitrogen vs air

Reply #2 –
Quote from: WS6_Keith –
Has anyone conducted such a test?  I know my rig has air in the tires now, and I see ~16-18psi increase from cold to hot on the fronts, ~ 10-12psi on the drives and ~10 on the tags.  I'm wondering if going to nitrogen would have less of a pressure increase and if so, any guesses as to how much?

Maybe.

If you have DRY air, there is very little difference between it an Nitrogen.  Both follow the Ideal Gas Law (PV=nRT).

If you have wet air/water in your tires (common from those convenience store coin operated pumps) there will be a greater difference as water vapor does NOT follow the Ideal Gas Law.

IMO, fill with dry air (like from your coach's on-board air system that has the air dryer and don't worry about it.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Tire pressure increase cold vs hot, nitrogen vs air

Reply #3 –
I used to fill my 5th wheel's tires with Nitrogen in the fall when we started headed south. It was nice always having the same pressure as we travelled through various climates and elevations in the high desert from Boise to Phoenix/Q. I ultimately decided it wasn't worth the hassle of finding it though and that's doubly true with the coach now.
1987 Grand Villa ORED
2001 U320 4010

Not all that wander are lost... but I often am.

Re: Tire pressure increase cold vs hot, nitrogen vs air

Reply #4 –
Quote from: Elliott –
I used to fill my 5th wheel's tires with Nitrogen in the fall when we started headed south. It was nice always having the same pressure as we travelled through various climates and elevations in the high desert from Boise to Phoenix/Q.

Elliott,
Are you comparing Nitrogen with the (wet) air that comes out of compressors without an air dryer?  If so, agree (physics) that there will  be a less change in PSI for a given temperature change with Nitrogen.

But, with any "content" in the tires, just short of 200 years of physics says there WILL be a PSI change with temperature change.

http://www.google.com/search?q=+PV%2B+nRT&client=firefox-b-1-d&ei=C7fFY-i-JfKIwbkP3vC8iAM&ved=0ahUKEwio8LOi-sz8AhVyRDABHV44DzEQ4dUDCBA&uact=5&oq=+PV%2B+nRT&gs_lcp=Cgxnd3Mtd2l6LXNlcnAQAzIFCAAQkQIyBQgAEJECMgkIABAHEB4Q8QQyCQgAEAcQHhDxBDIJCAAQBxAeEPEEMgkIABAHEB4Q8QQyCQgAEAcQHhDxBDIJCAAQBxAeEPEEMgkIABAHEB4Q8QQyCQgAEAcQHhDxBDoKCAAQRxDWBBCwA0oECEEYAEoFCEASATFKBAhGGABQgQVYgQVghQ1oAXABeACAAesCiAHrApIBAzMtMZgBAKABAcgBCMABAQ&sclient=gws-wiz-serp
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Tire pressure increase cold vs hot, nitrogen vs air

Reply #5 –
Quote from: wolfe10 –
Elliott,

Are you comparing Nitrogen with the (wet) air that comes out of compressors without an air dryer?
Yes, it was "wet" air, so the fluctuations were pretty noticeable that time of year going in and out of the eastern Sierras.

1987 Grand Villa ORED
2001 U320 4010

Not all that wander are lost... but I often am.

Re: Tire pressure increase cold vs hot, nitrogen vs air

Reply #6 –
Elliott:  Here is a combined formula for ideal gas law,

P= (PTV)/(TV)
Where;
P=Pressure
T=Temperature -- BUT for accurate results Temperature must be measured in Kelvins.
V=Volume

You read the formula Pressure equals Pressure times Temperature time Volume DIVIDED BY Temperature time Volume.
If you keep the volume the same size you can throw those terms away.
Use the same unit of measure for both pressure and volume.

Wanna do proportions?
1992 Foretravel Grand Villa
U225 SBID Build No. 4134
1986 Rockwood Driftwood
1968 S.I.A.T.A. Spring
1962 Studebaker Lark
1986 Honda VF700C
1983 Honda VF750C
Charlie, the Dog was broken out of jail 24 Oct 2023
N1RPN
AA1OH (H)e who must be obeyed.

Re: Tire pressure increase cold vs hot, nitrogen vs air

Reply #7 –
The primary purpose of selling compressed nitrogen for tires, is to compress our wallets!
Tim Dianics
Pam Sapienza
Vader PupZilla Labrador Canine Beast (AKA Pup)
Columbia, MO
1996 U320 4000
2021 Jeep Gladiator, Diesel

Re: Tire pressure increase cold vs hot, nitrogen vs air

Reply #8 –
Keep in mind that tire inflation recommendations are "Cold" pressure. They allow for the pressure increases due to temperature. That increase doesn't happen with nitrogen.
Bruce, Linda, and Macy
Zoey RIP 1/20/19
1999 U295 40' build #5400
2017 silver Jeep Wrangler, 1260 watts of solar on top
Moving around the country

Re: Tire pressure increase cold vs hot, nitrogen vs air

Reply #9 –
Quote from: bbeane –
Keep in mind that tire inflation recommendations are "Cold" pressure. They allow for the pressure increases due to temperature. That increase doesn't happen with nitrogen.

Actually it does.

Defying the Ideal Gas Law is only something Nitrogen salesmen dream about and mislead with.
Brett Wolfe
EX: 1993 U240
Moderator, ForeForum 2001-
Moderator Diesel RV Club 2002-
Moderator, FMCA Forum 2009-2020
Chairman FMCA Technical Advisory Committee 2011-2020

Re: Tire pressure increase cold vs hot, nitrogen vs air

Reply #10 –
It all started because Cup cars filled their tires with nitrogen . Why? Cuz we used nitrogen bottles to run the air guns .
Then some science guy says that the molecule is larger and clean gas has less moisture in it and this it will build less pressure at the same temp.  It dies build a pound less pressure . 
It will leak slower. Not required for most  situations  imho

Re: Tire pressure increase cold vs hot, nitrogen vs air

Reply #11 –
Unless one fills the tire when it's off the bead under a vacuum. Then filled with nitrogen. You are going to have 'some' air in it.

Just check and adjust pressure before a long drive and you should be good.

Or, one can whip out those slide rules and over analyze and adjust the pressure for that extra can of soup you put onboard and spike your blood pressure worrying too much about such things.
Jerry & Nona and Kimeru the cat that thinks she's a dog
1998 36' WTFE U320  #5314 Motorcade #17711
USAF 1975-1995
2019 Subaru Crosstrek 'toad'
2003 Subaru Legacy touring car
jerry Fincher | Flickr

Re: Tire pressure increase cold vs hot, nitrogen vs air

Reply #12 –
Quote from: wolfe10 –
Maybe.

If you have DRY air, there is very little difference between it an Nitrogen.  Both follow the Ideal Gas Law (PV=nRT).

If you have wet air/water in your tires (common from those convenience store coin operated pumps) there will be a greater difference as water vapor does NOT follow the Ideal Gas Law.

IMO, fill with dry air (like from your coach's on-board air system that has the air dryer and don't worry about it.
Always hated PV-nRT
Never know which n to use  LOL
1995 U-240 GrandVilla 36'
FMC# 18675
Lookingglass, OR
"There are four boxes to be used in defense of liberty: soap, ballot, jury, and ammo. Please use in that order." - Ed Howdershelt Abintra Press "If you have to lie to gain Support, you are not worth Supporting" "I just want to go somewhere where there's chocolate and nobody talks." - Ynez Reinschmidt

Re: Tire pressure increase cold vs hot, nitrogen vs air

Reply #13 –
I was having the same thoughts as well as I get ready to purchase a new set of tires. My thought on this was. If I'm supposed to change tires every 5 years I see little if any advantage of going through the hassle of nitrogen filled tires. I carry a small tank now for the Jeep that came with nitrogen filled tires. Doesn't take up much space and last almost a year. Carrying something big enough to service the coach tires is out of the question for me. Maybe some truck stops would have it available but I doubt it would be free.
As far as the pressure increase. I would guess the engineers accounted for that. Class 8 trucks have been on the road a long time using truck stop air I'm guessing.
2008 Nimbus 342
Build# 6464
ISM 500
Allison 4000 w/retarder
2021 Jeep Grand Cherokee

Re: Tire pressure increase cold vs hot, nitrogen vs air

Reply #14 –
Quote from: Res777 –
If I'm supposed to change tires every 5 years I see little if any advantage of going through the hassle of nitrogen filled tires.

As Protech Racing has pointed out, this nitrogen gas nonsense began when people who need to service their equipment track side started carrying a bottle full of nitrogen gas pressurized at better than 2,000 PSI because it was easier than schlepping an air compressor and looking (fighting) for an electric outlet to power the compressor.
1992 Foretravel Grand Villa
U225 SBID Build No. 4134
1986 Rockwood Driftwood
1968 S.I.A.T.A. Spring
1962 Studebaker Lark
1986 Honda VF700C
1983 Honda VF750C
Charlie, the Dog was broken out of jail 24 Oct 2023
N1RPN
AA1OH (H)e who must be obeyed.
 

Re: Tire pressure increase cold vs hot, nitrogen vs air

Reply #15 –
At this point I decided to fill just the front two tires with nitrogen.  Previous trips have shown 15-16psi increase from cold to max (110-126).  Unfortunately my Q trip was cancelled, but after my next trip I'll report if there is any significant difference in pressure rise with the nitrogen.

BTW, it took 1400psi from the bottle to fill each tire.
Keith
2003 U320 38' #6197