Nitrogen in tires

[MintJulep]

I figure the topic is safe here in the tech side....

I now have nitrogen in my tires.

I didn't ask for it. It just came along in the "deal" with the ridiculously expensive set of new run-flat tires on the Mini.

Free nitrogen fill-ups for the life of the tires even. And the best part Green valve stem caps.

 

[patprimmer]

with the ridiculously expensive set of new run-flat tires

So it was really far from free.

A set of the best of the "made in China" tyres would perform well enough so you would never notice a difference and you would have saved enough to get a new tyre and wheel delivered by cab if ever you needed it.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[VEBill]

I've always been satisfied with 80% nitrogen.

One of the "advantages" touted for nitrogen-filled tires is that the nitrogen is supposedly very dry. This seems a bit pointless since the tire installer slops large quantities of soapy water onto the tires' beads during installation, leaving plenty of dribbles inside the tire. Perhaps they should replace the soapy water with snake oil...

 

[arunmrao]

For the past 3 years I have Nitrogen filled tubeless tyres. The drive is comfortable considering Indian road and traffic conditions. I need to pay about 1USD every time I go for a refill ,also there are very few nitrogen filling centres .

_____________________________________
"It's better to die standing than live your whole life on the knees" by Peter Mayle in his book A Good Year

 

[zdas04]

Does anyone know the benefit of nitrogen vs air? I know you are getting rid of a bit of oxygen inside the tire, but there is still measurable oxygen outside the tire so it can't be an oxidation reaction with the rubber, can it?

The nitrogen should be noticeably dryer than atmospheric air (although, where I live the normal humidity is under 12% so here it wouldn't be a lot). If moisture is that big a problem, desiccant beds do a good job of getting the dew point really low for a lot less than a buck a fill.

I can't work out a reason for it.

David

 

[VEBill]

It's an obsessive compulsive type psychological defect that I would call 'the false finishing touch'.

Basically the same thing as putting a six-inch diameter tail pipe on a clapped-out $1200 Honda. Or agonizing about the 'directionality' of the speaker wires on one's home theatre.

These sorts of 'false finishing touches' almost always falsely imply that the system in question (car, stereo, etc.) has reached a level of technological "perfection" that it actually makes sense to worry about such inconsequential nonsense.

 

[BigInch]

Contact me about N₄. I guarantee that it will get 200% better performance than any of those foolish tires using simple N₂.

Let your acquaintances be many, but your advisors one in a thousand’ ... Book of Ecclesiasticus

 

[ivymike]

what a coincidence, a coworker of mine reported getting a nitrogen fill yesterday... since he's in accounting I walked him thru the utter nonsense of it on our walk from the parking lot & elevator ride. He remarked "at least I didn't pay for it" and I just didn't have the heart to say "oh yes you did!"

 

[JJPellin]

I have a friend at work that is fortunate enough to own a new Jaguar. One day he had a tire that was a bit low. He would not even consider adding air. In fact, he would not accept nitrogen from any source but the Jaguar dealer. He had been told that he needed to use only Jaguar brand nitrogen. He was afraid it would affect his warranty if he got inferior nitrogen anywhere else.

Johnny Pellin

 

[pmover]

got lucky and the write-up clarifies the matter for me. keep in mind that nascar folks race in high humidity areas.

meanwhile, i hope this helps.

http://auto.howstuffworks.com/auto-racing/nascar/nascar-basics/nascar5.htm

-pmover

 

[zdas04]

OK, so it is a technician solution to excessive moisture in compressed air. The engineering solution would be to run the air through a desiccant bed. Thanks for the link pmover.

David

 

[ozmosis]

FYI:

http://www.motoringweekly.com.au/technology/tyres/nitrogen_tyres.html

 

[patprimmer]

I agree with everything in the article osmosis linked to.

The main reason for nitrogen in MASCAR is because they have a bottle of compressed nitrogen handy and it is safer to transport than air.

Dry is important to aircraft as they fly at altitudes where ambient is considerably below freezing and any water vapor first falls out as condensation then freezes.

Lumps of ice that never had time to melt are a problem.

Re oxidation, as the outside of the tyre is exposed to heat and sunlight and air, it will oxidise more than the inside and even so very few tyres fail from rubber degradation.

Isaac

As you are an engineer you could be expected to have expert technical knowledge than the accountant, but it must be a real concern when he fails in his area of expertise of allocating costs

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[zdas04]

Pat,
Could you explain the idea that compressed nitrogen is "safer to transport than air"? I can see "more convenient" since you can purchase a large nitrogen bottle from an industrial supply house that is under pretty high pressure. To get your bottle filled to the same pressure with air you would only have to purchase a compressor like they use to fill scuba tanks.

Neither nitrogen or air is particularly corrosive on its own, neither is flammable on its own. A nitrogen leak in a confined space can create an oxygen poor environment that can be lethal. An air leak in a confined space is just air. Both present a compressed gas hazard in storage, but for the same volume at the same pressure that risk is identical for the two.

When I look at the options, nitrogen has one downside that air doesn't. Air has zero downsides that nitrogen doesn't. It looks to me like the reason comes down to availability of refills at sufficient pressure, not safety.

David

 

[ivymike]

So how much pressure change would you expect in a tire due solely to the presence of water? I'm not convinced it would be measurable... maybe I'll be motivated enough to estimate that myself later on.

 

[patprimmer]

I was of the impression that pressure increased the reactivity of the oxygen in air, but I must admit it was a vague recollection.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[VEBill]

Do the tire monkeys at your local tire shop meticulously avoid getting any soapy water dribbling down inside the tire when lubricating the bead during the installation of the tire onto the rim? The local tire shops around here, even the ones that use N2, certainly don't. They slop the water onto the bead leaving plenty of dribbles inside the newly installed, N2 filled, tire.

Do they purge the tire several times with pure dry N2 to reduce the ratio of "moisture laden" ambient air that was inside the tire at the start? Given PV=nRT at 30PSI, there's still about one-third moisture laden air inside. It would require two (10-minute +/-) purge cycles to reduce the ratio of air in the "N2 filled" tire to less than 10% of ambient.

These inconsistencies reveal that the moisture theory, as applies to your local tire shop, is a poor lie.

 

[ivymike]

if you assume that the tire was completely dry inside before air was added, and that the air in the shop tank was at 125F, 100psi, and saturated with water (excess water was drained off), then you get about 1.1% of the mass into your tire being water vapor.

if I'm doing the math correctly, your tire pressure would behave as follows with the moist air (tire internal volume held constant for simplicity):
@ 0F, 24.3 psi
@ 32F, 27.2 psi
@ 68F, 30.5 psi
@ 125F, 35.9 psi
@ 150F, 38.0 psi
@ 200F, 42.3 psi

If you made all the water disappear to leave dry air (reducing the mass in the tire), that would be:
@ 0F, 24.3 psi (0.0 psi less)
@ 32F, 27.1 psi (0.1 psi less)
@ 68F, 30.1 psi (0.4 psi less)
@ 125F, 35.0 psi (0.9 psi less)
@ 150F, 37.1 psi (0.9 psi less)
@ 200F, 41.4 psi (0.9 psi less)

So there would be a slight difference... not sure it's an important one.

 

[patprimmer]

So in reality, compressed ambient air on a typical day at a typical race track might cause the tyre to run 0.5psi higher than one filled with nitrogen if the tyre was well purged.

The real difference is the comparable pressure change that might normally occur due to changes in temperature of the tyre while racing as they would set the cold pressure to give the best hot pressure.

On a road car anyone who can pick or measure the influence of 0.5psi difference is kidding.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

http://eng-tips.com/market.cfm

for site rules

 

[zdas04]

I'm thinking that there are three categories of tires that should be considered.

Tires on the family truckster--nitrogen doing anything beneficial is an urban legend. It is simply a waste of money and a possible health hazard to the pump monkeys in a tire shop
(storing nitrogen bottles in a confined space under the control of idiots has a real potential to create an oxygen deficient atmosphere).

Tires on a race car--might be more convenient for professionals to get and haul nitrogen bottles than hp air tanks. Convenience and economics controls here, not performance.

Tires on airplanes--high-humidity air could easily have excessive condensation during high altitude flight. Taking this mass out of the gas phase will lower the pressure in the tire (liquid water takes a lot less space than water vapor), and could create dangerously low tire pressure on landing. This seems like a stretch to me, but I haven't done the math.

David