Tire pressure while driving - Montana Owners Club

Minitrbo · 03-09-2020, 10:19 AM

Weeks ago I had a tire blowout. I replaced all the OEM F rated tires with G rated Carlisle. Subsequently I installed a TPMS. The cold pressure in each tire is 110 psi as recommended for the load. When driving in 65 F weather at 65 mph I saw the pressure get as high as 135 psi.

A lot of forums say things like "I believe ..." and so on. I'm interested in finding out if anyone knows for a fact, such as a data sheet from a manufacturer, at what pressure I should become concerned. FWIW the maximum temperature reported by the TPMS is 90 F.

rohrmann · 03-09-2020, 11:12 AM

The tires are designed to handle the pressure rise when driving. Just make sure you check pressure when the tires are cold, like in the morning prior to driving.

mlh · 03-09-2020, 12:29 PM

You do NOT haft to worry about a pressure rise. The tires are designed to handle that. Inflate then to 100 to 110 and don’t worry.
Lynwood

Chasnracin · 03-09-2020, 01:32 PM

As everyone has stated, they are rated for the increase in temp. That being said, if you have one that is increasing greatly, check out why. Possibly axle allignment, bearing heat, or maybe just under your heaviest slide causing it.

**DQDick** · 03-09-2020, 02:36 PM

I would be concerned about 135. I had a couple of G 614's get that high once and one of them failed. I think it was a combination of a large change in both temperature and altitude at the same time. The tires were also 6 years old and I wouldn't let that happen again either.

Slow Hand · 03-09-2020, 05:33 PM

Just wait for a 100 degree day then check LOL

timandsusan · 03-10-2020, 08:02 AM

Yes, I would be concerned about 135 degrees on a 65 degree day. What was your speed? It is basic thermodynamics. Put 65 degree water in a pot and put it on the stove but do not turn on the stove. What will be the temperature in 1 hour?? It will be 65 Degrees. Now, turn the stove on to 100 degrees. What will be the water temperature in an hour?? 100 degrees MAXIMUM! It cannot boil! So how does the tire get to 135 degrees?? I would say that it is tire flexing causing the air temperature in the tire to increase. I think the 135 is a big issue. As an engineer--I did study thermodynamics! Either the temperature reading is in error-a possibility or the tires are defective.

Minitrbo · 03-10-2020, 11:16 AM

As an engineer who has studied thermodynamics and chemistry, which perhaps is not all that important methinks, since like playing telephone in grade school we lost track of the thread. The original topic was concern about tire PRESSURE measured in pounds per square inch, not tire TEMPERATURE. The peak TEMPERATURE I observed was 90 F. It was the pressure reported of 135 PSI for which I was concerned. Speed: 65 mph maximum.

mlh · 03-10-2020, 12:06 PM

As an engineer you should know pressure and temperature go hand in hand.
Lynwood

drjjj · 03-10-2020, 03:23 PM

While traveling through AZ in 2018 my G614's all got to 135-138 with no ill effects. It was hot outside. I did notice that if I slowed from 65 to 60 that the temperature dropped 3-5 degrees. As other posters have said, I would be more concerned about one tire being significantly higher than the others on the TPMS.

mhs4771 · 03-10-2020, 03:29 PM

Question: Did you see this same increase in all four tires?? If only on one tire, I would be very worried.
To be honest I haven't heard good things about Carlisle Trailer tires, most are using either Goodyear or Sailun. But knowing nothing about Carlisle tires, the 25 pound increase might be normal.
I have run Goodyear 17.5 H's and now Sailun 17.5 H's and on a warm day will generally see a 25 pound increase from the set pressure of 125.

Slow Hand · 03-11-2020, 04:21 PM

You don't think the engineers at Goodyear tested these tires to Way more heat and air pressures that are marked on the tires. Ever wonder why they say to check tire pressures when the tire is cold. I bet these tires could stand 200PSI before they fail. If you drive in the desert on a 130 degree day you ever wonder what the PSI's in the tire would get to.I bet these tires have been subject to higher temperatures than that. After all peoples lives are at stake

Code80 · 03-15-2020, 01:24 PM

I have been thinking about getting my 5th wheel tires filled with nitrogen. Nitrogen is not effected by temperature. One place wanted $15.00 per tire and that seemed reasonable.

Fish · 03-15-2020, 01:32 PM

Quote:

Originally Posted by Code80

I have been thinking about getting my 5th wheel tires filled with nitrogen. Nitrogen is not effected by temperature. One place wanted $15.00 per tire and that seemed reasonable.

I think that's a huge racket. I had nitrogen in the tires on a truck I bought once, the tire pressure still went up and down.

Then you have to find nitrogen to add if you need it, not so easy to find sometimes.

Code80 · 03-15-2020, 01:37 PM

Had it in our car, no issues stayed the same summer and winter. I think it really depends on the people putting it in and if they evacuated the air correctly.

kowbra · 08-05-2020, 11:14 AM

Quote:

Originally Posted by Fish

I think that's a huge racket. I had nitrogen in the tires on a truck I bought once, the tire pressure still went up and down.

Then you have to find nitrogen to add if you need it, not so easy to find sometimes.

Not my experience -at all... in fact I would say nitrogen has been a game changer for me.

Short version:
-a fraction of variance in pressure due to sitting or temperature changes
-significantly longer tire life

Long version:
I have now had nitrogen in my last couple pickups for over 8 years, and my last RV for 3 years. My tires go from -40F at home in winter to over 110F in AZ late spring. I add air maybe once per year to my RV and a couple times per year on the truck. (that's about 10,000 miles per year on the RV, and 25,000 on the truck). This past winter, checked tires on the RV at -35F before the trip south, and after sitting for over 3 months in AZ, checked them again. The pressure had increased by about 2lbs, so a few seconds to bleed off and good to go.

Before nitrogen, I checked air every couple weeks and usually had to air up or air down when temps changed more than about 20 degrees one way or the other. Prior RV had E rated tires, and on 80lbs with straight air, could easily see pressures lose 5lbs or more after sitting a few weeks... or increase by 5lbs+ if ambient temps went way up.

I don't have a TPMS on the trailer, and since going to nitrogen have had no flats. And, again, a normal pretrip is to check all tires, then usually needing to do nothing further. I may go to TPMS on the new Montana, but again nitrogen has been good to me without it.

BTW, I top up with 78% nitrogen from my Viair when on the road, don't worry about adding the "special stuff". I know I'm diluting and eventually would lose the value of paying for the initial nitrogen... but again the need to add air is so rare that in 4 years on the truck and 3 on the last RV I haven't observed tire pressure changes varying more than when first installed.

One last thing; last truck I went over 50,000 miles on the factory Firestone tires, towing about 30,000 miles of that. 3 year old RV tires look new. Both are much better results than units before nitrogen.

So, I'm a fan, and will continue to pay the small price to have it done every time I buy new tires.

Of course, I present a sample size of 1, and YMMV ;-)

Brad

Mikelff · 08-09-2020, 01:30 PM

Quote:

Originally Posted by Code80

I have been thinking about getting my 5th wheel tires filled with nitrogen. Nitrogen is not effected by temperature. One place wanted $15.00 per tire and that seemed reasonable.

The deal with Nitrogen, if you took high school chemistry, is that the molecule is larger than o2 and therefore will hold pressure in tires longer. Tires are porous and over time loose pressure from o2 escaping through the walls of the tire. Nitrogen is also less affected by heat causing increased pressure, though pressure will increase with heat, but not as much as O2, thus tires will run cooler. Nitrogen is also less affected by altitude. This is one reason all aircraft tires are nitrogen filled. If you cannot find nitrogen to top off your tire pressure, just use regular air, you will be fine. My local Cosco uses nitrogen and fills my tires for free. $15 for nitrogen filled tires is definitely NOT wort it in my view, but that is your call. Thats the basics for nitrogen filled tires.

kowbra · 08-09-2020, 01:38 PM

Quote:

Originally Posted by Mikelff

The deal with Nitrogen, if you took high school chemistry, is that the molecule is larger than o2 and therefore will hold pressure in tires longer. Tires are porous and over time loose pressure from o2 escaping through the walls of the tire. Nitrogen is also less affected by heat causing increased pressure, though pressure will increase with heat, but not as much as O2, thus tires will run cooler. Nitrogen is also less affected by altitude. This is one reason all aircraft tires are nitrogen filled. If you cannot find nitrogen to top off your tire pressure, just use regular air, you will be fine. My local Cosco uses nitrogen and fills my tires for free. $15 for nitrogen filled tires is definitely NOT wort it in my view, but that is your call. Thats the basics for nitrogen filled tires.

Great explanation, thanks!
Agree with all of the advantages, and in my case has translated into no issues with flat tires since converting, many more miles of tread life, not needing to obsess about tire pressures every trip, etc.

So, I'm curious why you think that's not worth $15 per tire?

Brad

Mikelff · 08-10-2020, 08:59 AM

Hi Brad, I guess it’s a personal choice and what it’s worth to you. In most cases, with cars anyway, it’s not worth the expense and hassle. With high pressure tires like most of us run on our 5ers (80 psi and up) it does have some benefit in my opinion . I have used nitrogen filled tires for years in my airplane as required. The reason is because of altitude and related pressure swings in tires and to prevent wheel hang up with the landing gear and having a tire get stuck in the well. Mine don’t retract so I don’t have that issue. I find my tires run cooler, especially in hot weather , and keep a more constant pressure, especially going through the mountains. I get my tires filled for free at my local Costco or the airport. I only run nitrogen in my RV, not my truck. Eventually you will need to add a little nitrogen to bump up your pressure, your paying whatever for just a few pounds. You can add air in a pinch but when you are done with your trip, you need to evacuate your tire again and re-refill it to get the full benefit of using nitrogen. For me, it’s an easy fix at no cost, so I do it. Would I pay for it? Probably not. Again, its a personal choice and how much of a value you place on it. Hope that helps.

phillyg · 03-15-2020, 01:34 PM

Tire mfgrs state to set cold (not driven on) pressure. You don't have to worry about 135 degrees on all four tires. What you do have to be concerned with is if one tire is significantly higher than the other three, indicating a possible problem with that tire. Another possible tell-tale is if one axle's tires are hotter than the other, indicating that axle is carrying more weight for some reason.

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