Tire pressure when traveling

N-Trouble wrote:
Your fine. Max PSI on tire label is COLD so its expected that PSI will rise with temp.

Make that the maximum cold pressure at the maximum loading.

OP wrote:
I have the Tire pressure monitoring system < my tires are load range E and inflated to 80 PSI which is what is called for on the tires, when I am traveling they heat up to where the tire pressure is over 90 psi and that is with outside Temperature is in the 60 to 70 degree range, going south in November, I get concerned that the pressure is way to high, Opinion,s

I may be missing something here, but what are you driving? What size tires do you have? If you're driving a MH, 80psi cold seems low, and if it is too low for your weight, that could be why you get so much heat expansion.

N-Trouble wrote:

joshuajim wrote:

N-Trouble wrote:

Tom N wrote:

N-Trouble wrote:

You can use nitrogen in your tires if it makes you feel better as it is more stable than oxygen and will not raise the PSI as much as it heats.

???

Under equal pressures, all gases expand at the same rate. A gas expands by the same proportion as the temperature rises, provided external pressure remains the same.

True however nitrogen is a "dry" gas unlike oxygen which contains moisture, and as a result will not see as dramatic changes in PSI with temperature. This is one of the biggest reasons racers use nitrogen for consistent PSI across varying temps.

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=191

Still not correct. ALL bottled gasses are dry whether they be nitrogen, oxygen, argon or just about anything else. Pure gasses by themselves DO NOT contain any moisture. AIR, which is mostly nitrogen/oxygen is what contains water vapor, and even that can be almost dry if run through a refrigerated air dryer.

OK but you knew what I meant... Air, not oxygen. Compressed air contains moisture. There ya happy...

I know only what YOU SAID, not what you meant. Walked it back just like a good politician :)

There you have it. Any ole compressed air will do (it's free). And, it too is a science.
And, 118 psi in the fronts with 107 psi in all the rears works great,.... if you have what I have. The original tires are still on it, and have never had a problem. I carry a homeade air compressor arrangement that has a 3-1/2 hp Briggs/Stratton (I can lift it with one hand). And, I use a high-quality digital gauge (check them all the time, at ambient temp).
I'm in the process of replacing the tires, just in case there's something to the belief that RV tires should be replaced according to age. Also, if I could decide which one suits my needs, I would buy a pressure/temp monitor.

joshuajim wrote:

N-Trouble wrote:

Tom N wrote:

N-Trouble wrote:

You can use nitrogen in your tires if it makes you feel better as it is more stable than oxygen and will not raise the PSI as much as it heats.

???

Under equal pressures, all gases expand at the same rate. A gas expands by the same proportion as the temperature rises, provided external pressure remains the same.

True however nitrogen is a "dry" gas unlike oxygen which contains moisture, and as a result will not see as dramatic changes in PSI with temperature. This is one of the biggest reasons racers use nitrogen for consistent PSI across varying temps.

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=191

Still not correct. ALL bottled gasses are dry whether they be nitrogen, oxygen, argon or just about anything else. Pure gasses by themselves DO NOT contain any moisture. AIR, which is mostly nitrogen/oxygen is what contains water vapor, and even that can be almost dry if run through a refrigerated air dryer.

OK but you knew what I meant... Air, not oxygen. Compressed air contains moisture. There ya happy...

I'll tell you where the real problem is, that dam pressure monitor !!
Dare tell me there would be a problem, much less this stupid thread, if the pressure monitor didn't exist.
Same as the battery finatics that have way more battery problems than normal people, because of hydrometers !

The reason to use nitrogen that was stated to me: the molecules are larger resulting in slower loss of pressure.
I've purchased tires from Costco for years - I always pay quite a bit less than the prices at tire stores, and they fill 'em with nitrogen. Very rarely do I need to add air.

Would I demand or pay to have them filled with nitrogen over air if it was an option? No.

To the OP - check your weights, inflate your tires at or just above the recommended pressures for your weights, and enjoy your trip! I run 65 lbs in the rear duals and 60 in the fronts, with plenty of capacity and a comfortable ride.

THE IDEAL GAS LAW FORMULA might help explain why different gases expand at virtually the same rate as their temperature increases.
A gas may be completely described by its makeup, pressure, temperature, and volume. Where P is the pressure, V is the volume, n is the number of mols of gas, T is the absolute temperature, and R is the Universal Gas Constant,

P V = n R T

This formula is the "Ideal Gas Law Formula." Although there is no such thing as an ideal gas the formula is pretty accurate for N2, CO2, and oxygen as we assume that the gas molecules are point masses and the collisions of the molecules are totally elastic. (A completely elastic collision means that the energy of the molecules before a collision equals the energy of the molecules after a collision, or, to put it another way, there is no attraction among the molecules.) The formula becomes less accurate as the gas becomes very compressed and as the temperature decreases but here "very compressed" pressures are well above even the highest tire pressures and "decreased temperatures" are extremely cold, too cold for tires. There are some correction factors for both of these factors for each gas to convert it to a Real Gas Law Formula, but the Ideal Gas Law is a good estimation of the way N2, CO2 and "air" should react through temperature changes. What does all this mean? It simply means that "air", nitrogen vapor, and CO2 vapor should all react pretty much the same within normal tire pressures (0-120 PSI) and temperatures.


Above is from this site which will tell you more than you ever wanted to know about nitrogen in tires. Bottom line - it's a waste of money.

My question is why 80 PSI cold. Have you weighed the RV and checked an inflation chart? Over inflated tires ride harder and are more susceptible to road hazard damage.

As soon as nitrogen was mentioned, I knew the thread would take this nasty turn.

N-Trouble wrote:

Tom N wrote:

N-Trouble wrote:

You can use nitrogen in your tires if it makes you feel better as it is more stable than oxygen and will not raise the PSI as much as it heats.

???

Under equal pressures, all gases expand at the same rate. A gas expands by the same proportion as the temperature rises, provided external pressure remains the same.

True however nitrogen is a "dry" gas unlike oxygen which contains moisture, and as a result will not see as dramatic changes in PSI with temperature. This is one of the biggest reasons racers use nitrogen for consistent PSI across varying temps.

http://www.tirerack.com/tires/tiretech/techpage.jsp?techid=191

Do NOT fill a tire with oxygen.