Pumping Auto Tires With Nitrogen?

[Pyrotex]

Last night (January 16, 2008), one of our Houston TV channels, KHOU, gave a news report on the availability of nitrogen for pumping up car tires. The newsman suggests that using dry nitrogen in tires keeps them inflated longer because nitrogen is denser than air.

 

:) :hihi: :) :) :eek_big:

 

HELLO!!! Air is nearly 3/4 nitrogen already.

 

The newsman went on to say that there were only a few places where the motorist can fill their tires with nitrogen, and one of those places charges $40 to fill up four tires.

 

:eek_big: :eek_big: :eek_big: :eek_big: :eek_big:

 

FORTY BUCKS????

 

Now, dry nitrogen contains no oxygen or water vapor, and I can understand how that would increase shelf life for tubes (or even tires if they were packaged airtight) sitting in warehouses for months or years. But how can it maintain tire pressure longer??? The "density" argument is just stupid.

 

So, the question is, is this a scam or a hoax? How gullible is KHOU TV?

[Mercedes Benzene]

My guess is that it has some truth to it. I remember being told once that Nitrogen moves a lot more slowly through certain membranes.

 

I think the idea behind this is that the Nitrogen will diffuse more slowly through the tires, so they stay inflated longer...

...but this is just a guess.

[Pyrotex]

Even if what you say is correct, normal air is about 75% nitrogen already. I can't see how 100% N2 is gonna be that much better than 75% N2.

:)

[CraigD]

My guess is that it has some truth to it. I remember being told once that Nitrogen moves a lot more slowly through certain membranes.

That was my initial guess, too. I think I jumped to a premature conclusion. :)

 

In this 1997 “Cartalk” letter, Tom and Ray Magliozzi state that it’s the dryness – the absence of water vapor - of the gas that’s most important. Nitrogen is just a good, readily available, non-leaky, non-toxic gas to use.

 

With the water removed, the gas in the tire expands both less and more predictably than with plain, humid air, a good thing if you want your tires to have close to the same pressure hot as cold, which is ideal to get the most even wear and best all-condition performance.

 

According to Tom and Ray (though I view a bit askance the authority of folk who cast about references like “Formula One (i.e., Indy 500)”), high-speed race cars have been using nitrogen filled tires for a long time, for the latter reason.

 

A drawback I can see is that, unless the place that gives you the Nitrogen has a “top off” policy, people who’ve spent the $$s for a nitrogen-fill may be reluctant to check and refill their tires as often as they should. If you’re going to go with race-car technology in you street car, I’d say go all the way, and either get your garage to fill them frequently, or get your own compressed dry nitrogen and do it yourself. That, or sneak your streetcar into racecar garages for its regular maintenance – I wonder, do those things have schrader valves, or something weird and exotic? :hihi:

[CharlieO]

Having been a service manager for a large Ford dealership with a considerable heavy truck and RV business, I can remember being approached several times by salesmen of Nitrogen tire inflating equipment. They all had claims of longer tire life and more stable tire pressures, which were claimed to save money, provide safer travel, etc., etc.

 

I am also newly aware of a promoter seeking money for investment in a "patented" nitrogen inflating service, claimed to be in wide spread use in Europe for trucks and very profitable for the investors. For a friend, I advised him the claims are true to a degree, just not cost effective enough to be worthy of any commercial investment. I also could not find any use of nitrogen inflation equipment by European truck service centers. Might be, just not known among my British contacts. [i was also a former British Leyland cars service engineer.]

 

As a former chief tech inspector for a racing organization, when much younger, I was also aware of nitrogen inflation in the 1960s being promoted as a means of stabilizing tire tread contact areas during racing, by stabilizing variations in air pressure when extremes of heat were encountered. Ambient air contains water vapor in varied amounts, which can vary tire pressures in slight proportion to the amount of water vapor in the air used for inflation; when heated by use. One reason why some air inflation equipment utilizes water filtration systems; to dry the air.

 

One might remember on TV shows of car racing events when drivers were swerving back and forth during yellow flag caution periods to "Heat up the tires." This is done to reach the most effective tire pressure and heat the tread rubber, so as to obtain maximum contact and traction during restart. I can testify, from having spun off the track just after starting a test session at Sebring, to my great embarrassment, that cold tires could be like driving on ice. However, I never saw any nitrogen inflation equipment in use during many years of racing; in which I never won a race and became a much better mechanic.

 

Nitrogen tire inflation is helpful to a degree and it does have some limited advantages. It is as yet just too expensive for these very limited advantages and too troublesome to be cost effective in my opinion.

 

Hope this helps, just couldn't resist answering something wherein I had personal experience.

 

Regards, CharlieO

[Turtle]

As most tires are tubeless, they will contain 1 'volume' of air at 1 atmosphere pressure before filling with whatever gas, so even with nitrogen inflation to operating pressure, there is no guarantee that no water vapor gets in. (Unless you want to buy our portable inflation room with hydrostatic control!?)

[CharlieO]

TURTLE: Good, obvious explanation. I should learn from you to be less long winded. However, my experience dates from a time in which everyone used tubed tires. Then, water vapor from inflation with air with varied amounts of water vapor did have some effect, the tubes being empty of air when installed in the tires. Dates me.

 

Currently, I'd have to pass on nitrogen inflation being cost effective.

 

Regards, CharlieO

[CraigD]

As most tires are tubeless, they will contain 1 'volume' of air at 1 atmosphere pressure before filling with whatever gas, so even with nitrogen inflation to operating pressure, there is no guarantee that no water vapor gets in. (Unless you want to buy our portable inflation room with hydrostatic control!?B))

My guess is that you break the bead on the tire (push the sidewall inward until it no longer seals with the rim) then flush the air out with the dry nitrogen through the tire’s valve, but as I’ve never seen it done (nor, it seems, have even our resident pro mechanics), that’s just a guess, as likely to be wrong as not. Even if that’s the proper way to do it, there’s no telling if a particular service vender will chose to skimp and do it as Turtle describes.

 

I’ll have to find someplace that does nitrogen tire inflation, and check them out. I’d be willing to pay $40 just to satisfy my curiosity.

[Buffy]

This one sounds like a job for the Mythbusters!

 

You know, I promised my mom and dad I wouldn't do anything stupid after I got out of college. Sorry, Mom, B)

Buffy

[CharlieO]

TURTLE is correct in his observation regarding tubless tires, however, after surfing Google sites I found there were many companies offering nitrogen inflation devices that answered his concern. Seems some of these contraptions will first vacuum clean out any moist ambient air and then refill the tire with dry nitrogen, which answers the adding nitrogen to existing ambient air at one atmosphere question.

 

Most of these companies produce promos to convince car or tire dealerson on how much money the dealers can make after the public is scared silly with their warnings and public service announcements about underinflation dangers and the ability of dry nitrogen to improve tire life and save money.

 

Most are not cheap devices, but dealers are assured they will profit greatly.

 

However, at least one tire manufacturer is even more skeptical about the advantages of nitrogen in the family car.

 

Michelin officials recommend nitrogen only for tires used "in a high risk environment and/or when the user wants to reduce the consequences of a potential abnormal overheating of the tire-wheel assembly (for example in some aircraft applications)," according to a company statement.

 

But for all other tires in normal use, nitrogen "is not required and does not necessarily bring the expected benefit."

 

"It is true that the physical properties of nitrogen reduce the pressure loss due to the natural permeability of the materials of the tire and thus the broad use of nitrogen will in general assist motorists with pressure maintenance."

 

"Nevertheless, the existence of several other possible sources of leaks (tire/rim interface, valve, valve/rim interface and the wheel) prevents the guarantee of better pressure maintenance for individuals using nitrogen inflation."

 

* * * * * * * * * * * *

 

ALSO: Tire experts at Consumers Union, publisher of Consumer Reports magazine, neither endorse nor object to the use of nitrogen in tires. "Nitrogen is certainly safe to use in tires, and theoretically it does offer some benefits," spokesman Douglas Love said from Yonkers, N.Y.

 

* * * * * * * * * *

My conclusions: You can save the expense and be just as safe if you check your tire pressures regularly. Something I do regularly and I carry an air compressor in my vehicle with the intention of stopping to assist motorists; which I averaged about once a year.

 

There is NO difference between using ambient air and nitrogen in regard to gas mileage, unless one is too lazy to check their tire pressures on a monthly basis and regularly allows their tires to become underinflated while using ambient air.

 

The rate of air pressure loss compared to the rate of nitrogen pressure loss seems largely one of BS statements used as testimonials. While flying USAF aircraft, I was aware of the use of nitrogen both for tire pressures and the replacement of fuel vapors; to avoid inflight explosions. However, a number of light aircraft tires were regularly filled with ambient air for convenience, while others were filled with nitrogen due to this being more easily available where they were serviced. Over several years at one base, I observed no difference in tire pressure loss over time between ambient air and nitrogen, nor did any crew chief ever comment about there being any difference.

 

Cost Savings in thru extended tire life is another illusion, with no known difference between ambient air and dry nitrogen, albeit running on underinflated tires with either gas will certainly wear out the tread quicker.

 

Regards, CharlieO

[yabahoobuh]

Last night (January 16, 2008), one of our Houston How gullible is KHOU TV?

 

It's Texas. You expect any different ?

[InfiniteNow]

Yes. Big state, lots of available variance in population. :confused:

[TheBigDog]

Another twist on the theme comes from the world of Monster Trucks where the owner of Bigfoot was the first inflate the massive tires with Helium to reduce the weight and improve handling. I am not sure how much this actually helps but it is done.

 

Bill