Inflate your tires with Nitrogen?

[Ridgemanron]

Extends tire life, improves fuel efficiency, prevents under-
inflation, are some of the plus factors according to the
tire people I spoke to at Ganin Tire where I had a new tire
fitted today. Was told the cost would be $20 and that any
re-fills ever needed were free of charge. Of course, you have
to bring back the car to their location for any re-fills....which
should be few and far between according to them. In an
emergency you can use air but I was wondering, in addition to
the worth of having Nitrogen, if there are aerosal cans that are
sold and are able to be kept in the car for those 'infrequent'
re-fills.

[Dave]

Here's another thread:
http://www.elisetalk.com/forums/showthread.php?t=12096

[LotusLust]

hmmm...on one of our projects we move 6000psi nitrogen bottles around to fill the tires on the aircraft

[Hillgiant]

Be sure to rotate the air in your tires, too!

[shay2nak]

Costco does this. I bought a rear tires from there and they put in Nitrogen in dem tires.

[Beanie]

Nitrogen is inert (no reaction with rubber, unike O2), contains no moisture (so it expands less than "air" when heated... acts more like an ideal gas), and is cheap. Air is about 88% nitrogen, so I would think small pressure changes (thinking increasing) at the track would still give you almost 100% nitrogen.

[TTP]

I'm gonna put helium in my tires.

[Hillgiant]

Hydrogen!

[Beanie]

I think Noble drivers only use Helium in their tires. It's a Noble Gas.

[Racer X]

I realize you guys are joking, but:

Helium: Be prepared to refill your tires alot. My understanding is that tires are more permeable to helium than "air". While there may be some difference in weight, there will likely be little differnce in mass, so it won't help acceleration much if any.

Hydrogen: Does the Hindenburg mean anything to you? It will also likely have to be refilled often,... pray for no static electricity! Make sure everything is grounded before starting.

Unfortunately I think someone has tried both of these, and learned lessons from their experience. Although helium is low risk... just tire squeal is a much higher pitch

Greg

[TimMullen]

Originally Posted by Ridgemanron

Extends tire life, improves fuel efficiency, prevents under-
inflation,

It's really not worth it.

Nitrogen won't leak out quite as readily, but it's not that much different than plain old air (88% nitrogen).

Pressures are more constant, but that's a function of the dryness of the gas - moisture in the air causes the pressure to rise when it gets hot. Use dry air (filtered with the water removed) and you'd get the same pressure stability.

Improves fuel efficiency simply by keeping a constant tire pressure - check your tire pressures for the same effect.

Extends tire life - this really doesn't matter. Yes, the nitrogen will reduce the degradation of the inside of the tire, but the outside is still exposed to the environment. The tire will wear out or weather crack long before the inside will degrade from air instead of nitrogen. It may be important if you run a fleet of long haul trucks where the tires last 100,000 miles and then are re-capped 10 times in their life times. But not for normal everyday passenger/sports car tires.

$20 to fill up your tires? You still have air in the tire from the air that was captured when the tire was mounted. And $20 will by most of an air/water separator for you air compressor's air line.

Nitrogen is used in race cars where tire pressure stability is critical, but probably simply because it's easy to get a portable high pressure tank filled with nitrogen fairly cheaply - important at the track with out nearby electrical supplies for the air compressors.

My last set of tires for my Honda was filled with nitrogen at Costco. So far, the only difference I've noticed is the green caps they put on the tire valves. I still top the tires off with my air compressor. But I also didn't pay extra for the nitrogen...

[Jag89]

All Aircraft tires are filled with Nitrogen. But that's mainly to avoid having moisture in the tires. For an automobile you won't see that much benefit.

[etypeiii]

For non-racers, nitrogen is good if you have a collector's car that is rarely or never driven (thus does not wear the tires much or at all.) It can help preserve collector's tires, though having old tires can be dangerous, nitrogen or not.

I too do not see much use to pay $$$ for it, though if you already have the cylinder...why not. In that case it won't cost you much extra. Dry air as mentioned should give all the same benefits (other than the oxidation protection) for less.




DLY

[Tyger]

Originally Posted by Jag89

All Aircraft tires are filled with Nitrogen. But that's mainly to avoid having moisture in the tires.

I am curious why nitrogen is supposed to by drier than regular air (although I can't really see why moisture content is an issue). Is it just because it comes from a cylinder?

[azskycop]

Originally Posted by Jag89

All Aircraft tires are filled with Nitrogen. But that's mainly to avoid having moisture in the tires. For an automobile you won't see that much benefit.

Actually aircraft tires have to be filled with nitrogen because it does not expand with altitude. Bad things happen if you tire blows up in your wheel well at 20,000 feet.

[Terminus]

Originally Posted by azskycop

Actually aircraft tires have to be filled with nitrogen because it does not expand with altitude. Bad things happen if you tire blows up in your wheel well at 20,000 feet.

errr...
nope
Expands just like any other gas.
The dry part is the only critical part in this equation, and, as mentioned above, you can get dry air as well. We used to use dry nitrogen at the track instead of dry air because 3000PSI nitrogen fills were much easier to come by.

[azskycop]

Well I could be wrong about the expansion but that is what they teach us down there at that pilot'n school. I was just posting what I've always been told. If it expands like air then why do the tires not expand at altitude? I would think that would put increase the psi levels to more than the tire could handle.

[EdHahn]

Originally Posted by azskycop

Well I could be wrong about the expansion but that is what they teach us down there at that pilot'n school. I was just posting what I've always been told. If it expands like air then why do the tires not expand at altitude? I would think that would put increase the psi levels to more than the tire could handle.

As a pilot, I'm sure you understand that the pressure in the tires remains normal (with varience for temperature) - it's the air outside the aircraft that is losing pressure (with altitude). (Small note - the gas inside the tire will tend to have lower pressure with altitude as the temperature at altitude is also lower.)

The pressure difference between the tire and the outside air is what is read out on the pressure gauge.

For a tire inflated at, say, 30 psi gauge pressure at sea level (at ISO standard atmosphere), the maximum pressure difference possible would only reach 44.7 psi (30 psi gauge pressure + 14.7 psi atmospheric) if the tire were in a vacuum. The tire carcass is designed to take this extra pressure that comes from altitude. (Edit - provided the tire was inflated at the proper pressure - see below.)

Regardless, dry air or dry nitrogen are going to have essentially the same pressure characteristics with temperature, and the tire will experience essentially the same pressure differential for a given flight scenario.

It's the moisture (i.e. water vapor that is near transition between gas and liquid form) that causes large swings in pressure.

Finally, nitrogen is beneficial for long-term storage as it will not oxidize the rubber on the inside of the tire.

ed

[Follow-up]
I did some additional research into both tire failure accidents on aircraft as well as nominal tire inflation pressures for aircraft.

NTSB doesn't seem to have any failures of tires at altitude - all records I could find had tire failure occur on the ground or just after takeoff, where I'm sure you'd agree that heat and loading put the tire under heavy load.

Second, the B747 has a normal tire pressure of 75 to 200 psi (gauge pressure) depending on the aircraft load. Once airborne, of course, the pressure is much reduced from the load during taxi or takeoff (i.e. the tire carcass need only support the internal pressure of the tire, not the additional load of the aircraft weight). Therefore, it's doubtful that a tire would happen to fail at altitude, rather than immediately after takeoff and climb.

Even if you assumed the tire pressure stayed at 200 psi gauge as measured on the ground, the additional pressure from putting that tire in a vacuum is a maximum of 214.7 psi. (This would correspond to sitting a fully loaded B747 in a vacuum.) This small amount of additional pressure on the carcass is hardly likely to cause a tire failure in and of itself, given certification requirements.

ed

[Surferjer]

I was confused too. I thought climbing altitudes would drop pressures, not build them.

What a weird topic. I learn a lot of miscellaneous crap here on Elisetalk!

[TimMullen]

Originally Posted by Surferjer

I was confused too. I thought climbing altitudes would drop pressures, not build them.

It does. The air pressure around the tire drops, and since we measure the tire pressure relative to the surrounding air pressure, the fixed volume of air in the tire increases the tire's internal pressure relative to the air around it at altitude.

The problem as mentioned earlier is that the moisture in air turn to gas as it warms up - this directly increases the tire's internal pressure (kind of like water expanding hugely as it turns to steam).

By requiring nitrogen, which by the way it's manufactured is dry, air craft are assured of getting no moisture. Requiring "dry" air is more difficult. Where do you get "dry" air? The air that comes out of my air compressor is "dry" because it passes through a water filter/separator, but it still has a lot of moisture in it. Getting really "dry" air could require several thousand dollars worth of equipment, and the average person/mechanic wouldn't really understand the difference between the "dry" air from my compressor hose, and the really "dry" air processed via expensive machinery.

Besides, a very high pressure tank of nitrogen is relatively cheap and portable, and readily available. Compressed air in high pressure tanks is harder to come by - only place I know of is a SCUBA tank, and you have to have a SCUBA license to get one of them filled.