Tire pressure changes for no reason

[Astro14]

Yes there is lots of nitrogen in ambient air, so what? Using Nitrogen is all about eliminating the oxygen. Not quite sure why people refuse to understand that. It has less to do with more oxygen than it does Eliminating O2 down to a couple PSI. Eliminate to O2 and you eliminate the moisture content, and its the moisture content within the tire that contributes to the drastic changes in tire pressure. I choose the inert gas and get very little deviance in temp related pressure changes.

I don't "refuse to understand" anything. That highlighted statement is simply not true.

Basic chemistry - all gases, including 78% nitrogen - follow the universal gas law. Water vapor, at the temperatures and pressures at which car tires are operated, is included in that by the way. At high saturation, you can get some effects that vary from the ideal gas law. But we aren't talking about super high saturation, we are talking about filling with air - not water.

So, if you're looking for dry air - sure, use N2. But you can achieve the same effect by putting an inline drier on your compressor and changing the desiccant when it gets saturated..

Your N2 filled tire experiences precisely the same pressure changes that my 78% N2 tire experiences when exposed to the same changes in temperature. Nothing more "drastic" than that. The same. As it must be.

PV=nRT requires that N2 experiences the same change in pressure as dry air for the same change in temperature.

Further, N2 and O2 both carry moisture. You're not eliminating H2O by eliminating O2, I have no idea where that concept originated (N2 machine salesman, I suspect) but most N2 machines have a drier in the line.

Bottled N2 is sold dry. That's why we use bottled N2 on airplanes - it's dry. Both the dryness and the lack of oxygen (we don't want to support combustion when the tires are inside the airplane) are why airplanes use N2.

Airplane tires experience a large enough temperature change, from -65F to 250F in minutes, sometimes, seconds, that any moisture present can undergo a phase change, and that is what causes a big swing in pressures.

Your car is not experiencing temperature changes of that magnitude, but if you race, where you can get big temperature spikes, N2 might be worth it. Otherwise, dry air performs every bit as well, and with the same exact variation with respect to temperature as described by the equation above.

 

[4WD]

The old TPMS worked off of speed sensors - maybe that’s where the 25% comment comes from. Those in my newer units are pretty darn accurate and will hound you for small changes …
(pick up a slow leak early)
I get OnStar notices overseas on the GM’s and text the wife …
(roofing nails happen in the south - product of storms)

 

[vavavroom]

The old TPMS worked off of speed sensors - maybe that’s where the 25% comment comes from. Those in my newer units are pretty darn accurate and will hound you for small changes …
(pick up a slow leak early)
I get OnStar notices overseas on the GM’s and text the wife …
(roofing nails happen in the south - product of storms)

Japanese and European manufacturers are increasingly using Indirect TPMS that is based on ABS sensor data rather than pressure sensors in each wheel. My 2015 Mini uses direct TPMS with a sensor on each special tire valve. I can tell I'm low before the system sets off a flag. I'm only being told which tire is low. The pressure is not disclosed. I think it's off by more than 5 psi from the last TPMS reset when the flag comes up. The only time I got a flag was after I deliberately let a good amount of air out of a tire in an effort to check if the system was working. I check my tire pressure once a week via a handheld gauge. Over the years I have caught a number of slow leaks from foreign objects penetrating the tire carcass and from leaky valve stems. In 33 years of driving I have had one spontaneous blow-out with complete loss of presure of a rear tire at freeway speeds. No drama other than a lot of noise and a smoking hot tire spinning on a hot wheel.

 

[CapriRacer]

Yes there is lots of nitrogen in ambient air, so what? Using Nitrogen is all about eliminating the oxygen. Not quite sure why people refuse to understand that.....

Because companies that supply N2 equipment have done a good job of confusing the matter.

It has less to do with more oxygen than it does Eliminating O2 down to a couple PSI. Eliminate to O2 and you eliminate the moisture content, .......

No, you haven't. I'm not sure what the principle is called, but ALL gases will "dissolve" into all other gases - and that includes water vapor - aka steam.

and its the moisture content within the tire that contributes to the drastic changes in tire pressure. ....

I don't know of anyone who has actually done a demonstration, but the math suggests the pressure water contributes to the inflation of a tire is small - small enough to ignore except for cases like racing where small changes in pressure change the handling of the car.

I choose the inert gas and get very little deviance in temp related pressure changes.

Be careful here. If you meant deviations from the Ideal Gas Law, that's true.

But if you meant in absolute terms, No!! ALL gases follow the Ideal Gas Law at temperatures and pressures we humans experience - including tires.

 

[kschachn]

Eliminate to O2 and you eliminate the moisture content, and its the moisture content within the tire that contributes to the drastic changes in tire pressure. I choose the inert gas and get very little deviance in temp related pressure changes.

How does eliminating the oxygen eliminate the water vapor?

 

[Jetronic]

Nitrogen for passenger cars has made some people a lot of money.
And given many people a sense of security.
If it's good enough for race cars, and airplanes, it's good enough for a true salesperson.

What good is a sense of security? Especially if it's false? Either you want actual security or a sense of what it actually is.

 

[4WD]

Japanese and European manufacturers are increasingly using Indirect TPMS that is based on ABS sensor data rather than pressure sensors in each wheel. My 2015 Mini uses direct TPMS with a sensor on each special tire valve. I can tell I'm low before the system sets off a flag. I'm only being told which tire is low. The pressure is not disclosed. I think it's off by more than 5 psi from the last TPMS reset when the flag comes up. The only time I got a flag was after I deliberately let a good amount of air out of a tire in an effort to check if the system was working. I check my tire pressure once a week via a handheld gauge. Over the years I have caught a number of slow leaks from foreign objects penetrating the tire carcass and from leaky valve stems. In 33 years of driving I have had one spontaneous blow-out with complete loss of presure of a rear tire at freeway speeds. No drama other than a lot of noise and a smoking hot tire spinning on a hot wheel.

My sensors are in the tire - the better tire shops have kits to rebuild them when a new set of tires are mounted - they are sensitive and accurate …
all tire 4 pressures stay up on my dash at all times …
N2 in tires - not getting in that ditch - too much gas law at my job …

 

[vavavroom]

I haven't had any car that didn't require a TPMS service kit every time a tire was installed. I've had shops forget to reset the TPMS. The TPMS should be reset every time you adjust the tire pressure. 4 sensors getting jostled - round round round, they get around. I suppose checking tire pressure by hand along with checking oil and coolant level is just too much of a burden for the driving average bear.

 

[Mechanician]

What good is a sense of security? Especially if it's false? Either you want actual security or a sense of what it actually is.

Sshhh
They'll hear you, (see this) and lose what they paid for.
If you want to start an interesting thread - start a list of all the things people buy, and only receive a sense of security.
Here's a start
1. Brain supplements

 

[kschachn]

Sshhh
They'll hear you, (see this) and lose what they paid for.
If you want to start an interesting thread - start a list of all the things people buy, and only receive a sense of security.
Here's a start
1. Brain supplements

Many threads on that already. Perhaps you participated in them.

 

[vavavroom]

An N2 filling would work better with an indicator dry cartridge. Those are used in some mechanically-powered wristwatches. Those watches have either an argon or N2 filling in conjunction with a hygroscopic dry cartridge with a color indicator. This system at least doubles the service interval of the watch. The reason is decreased oxidation of the lubricants. During the service, the dry cartridge is swapped out for a new one and the case is filled with an inert gas. Some dive watches, like the Blancpain 50 Fathoms, have merely a color-changing service indicator that indicates a high humidity level. For car tires, N2 does not much sense unless you have a way to top it off with N2. Or you don't check your tire pressure and trust the electronic gremlins.

 

[krzyss]

How does eliminating the oxygen eliminate the water vapor?

Magic!

Or somebody mistook 02 for H2O and thinks that O from water vapour is eliminated along with O2 from the air.

Krzyś

 

[IcarusLSC]

It's doubtful your made in China gauge is even accurate within 1PSI except for maybe when brand new and in a lab fwiw...

 

[SubieRubyRoo]

I’m gonna say for all 4 to be the same, the ambient temp dropped 10F and 1 psi.

My friend Rey checks his tire pressure only upon replacement. We had an argument about it. Imagine how much more carefree he is, than we at Bitog

TPMS sensors do my worrying. Only time I ever really make any adjustments is when one tire ends up being more than 3psi different than the others after at least an hour of driving when I know all the temps have equalized. I don’t worry about day-to-day changes as one side sits in the sun and the other in the shade; I don’t worry about morning pressures, and I don’t worry about summer to winter pressures until all 4 are reading at least 5psi lower than the pressures I saw in summer. Then I bump them all back up to my target of 40psi cold.

 

[Mechanician]

Many threads on that already. Perhaps you participated in them.

I can't recall

 

[SaberOne]

A friend of mine never checks their's ! Their theory is the car info system will tell them when it is low. I am not that confident to rely on that! By that time it is waaayyyy too low!

Sadly, I know people who do just that, and my son was one of them. I was disappointed because I've always been hands-on with vehicles. But now that my son has a family, he finally gets it.

 

[rcs]

Well thanks so much everyone for your advice, thoughts, and time. I took it to the dealership and the fill valves leaked, they tested them with soap and were corroded, thanks to the salt we use in the winter here in Michigan. They saw the corrosion and showed me once they removed them and put the new ones in. And of course the batteries in the sensors were not working. That is why I do not rely on them and always use my Jaco digital and analog pressure gauges. Thanks again you are ALL my hero's for always being there for me to help me!