[Raccoon]

Originally Posted by gpa

Once a week is good if you don't use vehicles a lot. Else, once every 10 to 14 days is good enough.

Hehe... In the car I check only once in one to two months. In the bikes once in say 15 days. When a vehicle or tyre is new, I just keep increasing the gap until i find the pressure dropping... When I find the duration it takes to leak away say 2 psi, I note the period and make that my frequency of filling/checking pressure.

[hellstar]

Originally Posted by Raccoon

Hehe... In the car I check only once in one to two months. In the bikes once in say 15 days. When a vehicle or tyre is new, I just keep increasing the gap until i find the pressure dropping... When I find the duration it takes to leak away say 2 psi, I note the period and make that my frequency of filling/checking pressure.

now that a logical approach , similar to what i follow , i too observe and act on need basis , thats what i do

[gostel]

So much for the Nitrogen mantra. They use it to keep potato wafers crisp and charge me through my nose each time I feel like having a bagful.

Nitrogen itself may not be the messiah that we may like to believe. Only dry Nitrogen will work on the tyres. This means we are using Nitrogen to get rid of the other devilish stuff like moisture (water vapor in dignified terms) and carbon dioxide.

I don't know what exactly water vapor does except that it can make potato wafers soggy. But carbon dioxide is a gas that can get heated when subjected to compression-decompression cycles inside a rotating tyre.

I would not pay a hundred for filling my tyres as Nitrogen tank is not all that expensive. I also refuse to believe that Nitrogen is retained inside the rubber and oxygen leaks out preferentially; it sounds a bit far-fetched, even though my Chemistry was terrible in college. No its not about the gas molecules; I refuse to believe that the tube rubber has such great properties!

[Thad E Ginathom]

My physics was terrible (as was my maths) in school, but of all those formulae, one stuck in my head:

pv/t is constant.

That's pressure, volume and temperature. Any gas gets hotter when compressed!

[anupmathur]

Originally Posted by gostel

.... But carbon dioxide is a gas that can get heated when subjected to compression-decompression cycles inside a rotating tyre.
....

And Nitrogen will not? Or compressed air? Or Hydrogen Sulphide?

They each will get heated and each will expand to the same extent!

Adiabatic compression?

[freewheelburnin]

Use of dry air without water vapour can help retain tyre pressure.Water vapour tends to expand or contract according to the temperature.Nitrogen filling definitely protects metal rims especially when tubeless tyres are used.But in a car with alloy wheels it does not matter.

[watashi75]

Originally Posted by Thad E Ginathom

pv/t is constant.

Rather

PV=nRT

where
P=Absolute pressure of the gas, in Pa
n=Amount of substance, in mol
V=Volume of the gas, in m3
T=Absolute temperature of the gas, in K
R=Universal gas law constant of 8.3145 m3·Pa/(mol·K)

Let the debate begin. But, I never imagined people would find it interesting to debate on the effects of gas and hot air.

[Tempelhof]

Originally Posted by watashi75

Let the debate begin.

See my earlier Post:
http://www.team-bhp.com/forum/techni...ml#post1289422

[gostel]

anupji I agree with you (with the little that I remember about adiabatic stuff) but what I was trying to say is that carbon-dioxide can heat up a lot more than say nitrogen or oxygen. Perhaps I may be recollecting this wrongly so please correct me.

[watashi75]

Originally Posted by Tempelhof

See my earlier Post:
http://www.team-bhp.com/forum/techni...ml#post1289422

Please see my earlier Post too:
http://www.team-bhp.com/forum/techni...ml#post1452461

[automobilophile]

Well, initially i had a thought that, due to a difference in the density, you might get a better mileage (lesser weight). All other benefits like constant pressure, lower heat generation are not applicable to normal city use, and have alternative cheaper solutions.

I personally feel, checking the pressure on every visit to a fuel station is the easiest and economical way to get better ride, lower wear and better fuel economy too. This will also ensure pressure is constant most of the time.

Regarding difference in weight, I am not very sure if it is significant to change fuel economy figures. Can anyone put some light on this?

[psp62in]

IMHO, a lot of these Nitrogen Claims seem to be just GAS.
The difference between N2 nd O2 molecular weight and size is small to say that one will permeate preferencially through rubber over the other. Also I am not convinced with the other possible explainations (like water vapour or CO2). This seems to be a Pseudo-science.
To prove the benefits of N2 filling, better scientific tests with accurate measurements are required to be designed to see the repeatable results. So far I havnt seen any such tests.

[Thad E Ginathom]

Originally Posted by watashi75

Rather

PV=nRT

where
P=Absolute pressure of the gas, in Pa
n=Amount of substance, in mol
V=Volume of the gas, in m3
T=Absolute temperature of the gas, in K
R=Universal gas law constant of 8.3145 m3·Pa/(mol·K)

Let the debate begin. But, I never imagined people would find it interesting to debate on the effects of gas and hot air.

Goodness! I vaguely remember that there were a couple of laws about the behaviour of gas (Charles and Boyle come to mind, but those brain cells are long-since disused) that combined into a more complex one, which you have probably given.

The point is that all gases, oxygen, nitrogen or water vapour, get hot if compressed, or increase in pressure if heated.

But... do some gases expand more than others?

[Tempelhof]

Originally Posted by Thad E Ginathom

do some gases expand more than others?

Yes, that's the WHOLE point !!

Till we understand that, this thread will be alive and going round-and-round forever !!

[Tempelhof]

Originally Posted by psp62in

This seems to be a Pseudo-science.
To prove the benefits of N2 filling, better scientific tests with accurate measurements are required to be designed to see the repeatable results. So far I havnt seen any such tests.

See: Tires - Nitrogen air loss study: Consumer Reports Cars Blog

and

Nitrogen in tires - Q&A: Consumer Reports Cars Blog