[Hutt]

Now that the weather is turning a bit colder every day when I first take off in the mornings I get a single tire low message which is quickly followed by all tires low. After driving for about 4 or 5 minutes, if I reset the TPMS it will clear. Once the tires warm up a bit. I know 10 degrees in ambient air temperature can make as much as 1 psi change but I thought these tires came from the factory with nitrogen which should be immune to that effect. Does anyone know? Should I be having the TPMS checked out or just having air drained and fill the wheels with nitrogen? It's becoming a royal pain in the a$$...

[Razel]

They're initially not filled with nitrogen. Normal atmospheric air. Get a decent tire gauge, fill them so the front tires have 32lbs and the rear has 35lbs when you check them in the morning (IOW, fill them 2-3 pounds higher if you have to drive for sometime and the tires are warm when you get home). Once they're adjusted to 32/35, reset the TPM and drive. Unless you have a leak somewhere, you should be good.

[Lotus7]

Originally Posted by Hutt

Now that the weather is turning a bit colder every day when I first take off in the mornings I get a single tire low message which is quickly followed by all tires low. After driving for about 4 or 5 minutes, if I reset the TPMS it will clear. Once the tires warm up a bit. I know 10 degrees in ambient air temperature can make as much as 1 psi change but I thought these tires came from the factory with nitrogen which should be immune to that effect. Does anyone know? Should I be having the TPMS checked out or just having air drained and fill the wheels with nitrogen? It's becoming a royal pain in the a$$...

Nitrogen follows the normal laws of gas physics and expands with temperature rise and contracts when cooled. The dry nitrogen used to fill tires has a slightly lower rate of expansion than moist air (which is 78% Nitrogen already). The idea that you don't have to be concerned with tire pressure changes as temperatures change if you use pure Nitrogen is a pure fantasy.

As temperatures change you should adjust the cold tire pressures to spec. In colder weather you will have to add gas (your choice plain old air or pure nitrogen it makes almost no difference). When temperatures rise in the Spring you will probably need to bleed off some of it.

You should not reset the TMS monitor unless you fill your tires when cold. Resetting because of a pressure drop due to temperature means you're probably running at too low a pressure and will result in poor handling, increased tire wear and reduced gas mileage.

The idea that pure N2 in tires will eliminate the need to add gas or that it does not change pressure with temperature changes is absolute, pure nonsense and it is almost criminal for dealers, service stations and anyone else to propagate. It's pure B.S. and an extremely profitable SCAM for those who promote it.

The truly sad part is that most of the world's population has such a poor understanding of basic science, let alone physics, that scams like this are able to be foisted on the public. Truly sad!

[Hutt]

Thanks for the quick and detailed responses.

[GQX3]

Originally Posted by Lotus7

Nitrogen follows the normal laws of gas physics and expands with temperature rise and contracts when cooled. The dry nitrogen used to fill tires has a slightly lower rate of expansion than moist air (which is 78% Nitrogen already). The idea that you don't have to be concerned with tire pressure changes as temperatures change if you use pure Nitrogen is a pure fantasy.

As temperatures change you should adjust the cold tire pressures to spec. In colder weather you will have to add gas (your choice plain old air or pure nitrogen it makes almost no difference). When temperatures rise in the Spring you will probably need to bleed off some of it.

You should not reset the TMS monitor unless you fill your tires when cold. Resetting because of a pressure drop due to temperature means you're probably running at too low a pressure and will result in poor handling, increased tire wear and reduced gas mileage.

The idea that pure N2 in tires will eliminate the need to add gas or that it does not change pressure with temperature changes is absolute, pure nonsense and it is almost criminal for dealers, service stations and anyone else to propagate. It's pure B.S. and an extremely profitable SCAM for those who promote it.

The truly sad part is that most of the world's population has such a poor understanding of basic science, let alone physics, that scams like this are able to be foisted on the public. Truly sad!

Amen to that Scotty...

[Lotus7]

First: Apologies to anyone who might have been offended by the somewhat harsh tone of my previous post. Whenever I see or hear about innocent people being "conned" by car mechanics, salesmen, politicians, or financial wizards pushing "ponzi" schemes, my blood boils and I sometimes loose control of my normally relaxed demeanor.

Triggers for my abnormal behavior include: Tires filled with Nitrogen*, miracle gas line magnets, intake "vortex" generators, engine "ionizers", and the latest con: the cigarette lighter plug-in power filter that will improve your fuel efficiency by 18%.

You've been warned!

If it can't be confirmed by a double blind test, it doesn't exist!

*Excerpts from John Lucidi, the Product Sales Manager for Nitrogen Inflation for the FNS division of Parker Hannifin in Haverhill, MA. (a company that makes Nitrogen tire filling equipment and apparently is concerned about what the false claims as to the benefit of N2 inflation are doing to the industry).

This from an article in a trade magazine addressed to auto dealerships:

"Don’t continue to perpetuate a lot of the misconceptions about nitrogen to your customers, its not in your best interest."

NITROGEN ELIMINATES THE NEED TO REGULARLY CHECK TIRE PRESSURES. This is absolutely untrue. While nitrogen leaks through a tire at a slower rate than oxygen, that doesn’t eliminate the necessity of regular pressure checks. There are numerous issues (valve stem, puncture, rim seal) that can still cause major leaks within a tire and lead to unsafe driving conditions. Nitrogen will maintain pressure longer than tires filled with compressed air, but is not a substitute for regular pressure checks.

NITROGEN PROVIDES LONGER TIRE LIFE AND INCREASED FUEL ECONOMY. This is one claim
that informed consumers have trouble grasping, since compressed air is already made up of 78.1% nitrogen. This can cause some skepticism with informed customers. Minimizing underinflation will lead to longer tire life and increased fuel economy.

TIRES FILLED WITH NITROGEN ARE NOT AFFECTED BY TEMPERATURE. There is no significant
difference in expansion and contraction characteristics of nitrogen compared to air when moisture is absent, as long as the gases are dry in a fixed volume container such as a tire. Nitrogen and compressed air respond to changes in ambient temperature in a similar manner, a 1.9% change of pressure for every 10F change in temperature.

[paul386]

Originally Posted by Lotus7

Nitrogen follows the normal laws of gas physics and expands with temperature rise and contracts when cooled. The dry nitrogen used to fill tires has a slightly lower rate of expansion than moist air (which is 78% Nitrogen already). The idea that you don't have to be concerned with tire pressure changes as temperatures change if you use pure Nitrogen is a pure fantasy.

As temperatures change you should adjust the cold tire pressures to spec. In colder weather you will have to add gas (your choice plain old air or pure nitrogen it makes almost no difference). When temperatures rise in the Spring you will probably need to bleed off some of it.

You should not reset the TMS monitor unless you fill your tires when cold. Resetting because of a pressure drop due to temperature means you're probably running at too low a pressure and will result in poor handling, increased tire wear and reduced gas mileage.

The idea that pure N2 in tires will eliminate the need to add gas or that it does not change pressure with temperature changes is absolute, pure nonsense and it is almost criminal for dealers, service stations and anyone else to propagate. It's pure B.S. and an extremely profitable SCAM for those who promote it.

The truly sad part is that most of the world's population has such a poor understanding of basic science, let alone physics, that scams like this are able to be foisted on the public. Truly sad!

+1...

Nitrogen for racecars... not passenger cars. The only thing that is effective about putting nitrogen in your tires is the profit for the party performing the "service".

[Hutt]

To do so, it was not actually going to cost me anything. With that said is there ANY advantage to doing so or still just pass on it all together. I would imagine ANY benefit realized by pure N2 would be eroded the first time I top off with air.

[Lotus7]

Originally Posted by Hutt

To do so, it was not actually going to cost me anything. With that said is there ANY advantage to doing so or still just pass on it all together. I would imagine ANY benefit realized by pure N2 would be eroded the first time I top off with air.

There are slight advantages "sometimes". It mostly depends on the "quality" of the source of plain air you're comparing the dry N2 to.
Most "gas-station" or "service dept." compressed air has a small amount of water vapor, which depending on how much water is present, will allow the an air-filled tire to gain pressure slightly more rapidly as the temperature increases. However, most service station air supplys have air/water separaters, or filters that remove the water so that is not a significant factor. Lightly used home compressors usually have a large enough storage tank, that the water condenses out and is drained periodically so again, it's not usually a factor.

The lack of Oxygen in tires that contain only N2 means that there is slightly less loss of pressure due to the sidewall rubber permeability over very long periods of time. Pure N2 will "seep" through the tire's sidewalls about 0.8 X less then plain air. That means if an air-filled Summer tire looses 4 psi when it's sitting in a garage in storage for 6-months, it will "only" loose 3.2psi if it were filled with pure N2. You will still have to top-up the tire pressure. However, as strange as it seems, Oxygen will permeate the tire from the outside (even though the N2 pressure is higher inside the tire, and will mix until the N2 - O3 mix is about 94% N2 and 6% O2. That takes about 3 months.

As long as it doesn't cost you anything, there is no harm in having your tires filled with pure N2, and as you surmise, adding plain air will eventually negate the perceived advantages, however small or non-existent.
Filling tires with pure N2, does no harm.

The problem is the public misconception, reinforced by many auto service centers, that doing so relieves owners of the task of checking tire pressures. That's almost criminal!

Just remember to check the tires with a good gauge once a month (more when temperatures change drastically) only when the tires are completely cold (at the current ambient temp.), and to only reset the TPMS after you are sure the tire pressures are all correct.

I find doing that can help one find potential small tire punctures well before they reach the point of causing complete deflation.

Suppose, for instance all your tires were set to 32psi last month and in checking you find three of them at 31 psi (due to "normal" pressure loss) but one is at 29 psi (none of which will have triggered a TPMS warning).
I'd bet that the 28 psi tire has a small nail that is still in the tire causing a very slow, probably repairable leak. Checking tire pressures only takes a few minutes, once a month and is just as important as checking engine oil levels (which on the X3 is entirely out of the driver's hands now).