Go Back   Team-BHP > Under the Hood > Technical Stuff


Closed Thread
 
Thread Tools Search this Thread
Old 21st September 2009, 00:49   #601
Senior - BHPian
 
Raccoon's Avatar
 
Join Date: Jan 2008
Location: Poona
Posts: 1,832
Thanked: 105 Times
Default

Quote:
Originally Posted by gpa View Post
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.
Raccoon is offline  
Old 21st September 2009, 09:20   #602
Senior - BHPian
 
hellstar's Avatar
 
Join Date: Dec 2006
Location: Bangalore
Posts: 1,071
Thanked: 17 Times
Default

Quote:
Originally Posted by Raccoon View Post
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
hellstar is offline  
Old 24th September 2009, 20:56   #603
BHPian
 
Join Date: Jul 2009
Location: Navi Mumbai
Posts: 180
Thanked: 68 Times
Default

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!
gostel is offline  
Old 24th September 2009, 21:04   #604
Distinguished - BHPian
 
Thad E Ginathom's Avatar
 
Join Date: Jun 2007
Location: Chennai
Posts: 7,839
Thanked: 7,209 Times
Default

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!
Thad E Ginathom is offline  
Old 25th September 2009, 08:10   #605
Senior - BHPian
 
Join Date: Sep 2007
Location: New Delhi
Posts: 3,083
Thanked: 252 Times
Default

Quote:
Originally Posted by gostel View Post
.... 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?
anupmathur is offline  
Old 25th September 2009, 09:00   #606
BHPian
 
freewheelburnin's Avatar
 
Join Date: Oct 2007
Location: bangalore
Posts: 272
Thanked: 26 Times
Default

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.
freewheelburnin is offline  
Old 25th September 2009, 09:05   #607
BHPian
 
watashi75's Avatar
 
Join Date: Jan 2008
Location: Hyderabad
Posts: 518
Thanked: 7 Times
Default

Quote:
Originally Posted by Thad E Ginathom View Post
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.
watashi75 is online now  
Old 25th September 2009, 09:10   #608
BHPian
 
Tempelhof's Avatar
 
Join Date: Oct 2007
Location: Bangalore
Posts: 450
Thanked: 123 Times
Default

Quote:
Originally Posted by watashi75 View Post
Let the debate begin.
See my earlier Post:
http://www.team-bhp.com/forum/techni...ml#post1289422 (Inflating tyres with dry nitrogen)
Tempelhof is offline  
Old 25th September 2009, 09:20   #609
BHPian
 
Join Date: Jul 2009
Location: Navi Mumbai
Posts: 180
Thanked: 68 Times
Default

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.
gostel is offline  
Old 25th September 2009, 09:27   #610
BHPian
 
watashi75's Avatar
 
Join Date: Jan 2008
Location: Hyderabad
Posts: 518
Thanked: 7 Times
Default

Quote:
Originally Posted by Tempelhof View Post
Please see my earlier Post too:
http://www.team-bhp.com/forum/techni...ml#post1452461 (Inflating tyres with dry nitrogen)
watashi75 is online now  
Old 25th September 2009, 20:35   #611
BHPian
 
Join Date: Jan 2009
Location: Bangalore
Posts: 44
Thanked: 21 Times
Default

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?
automobilophile is offline  
Old 26th September 2009, 00:14   #612
BHPian
 
Join Date: Oct 2004
Location: Mumbai
Posts: 175
Thanked: 17 Times
Default

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.
psp62in is offline  
Old 26th September 2009, 00:38   #613
Distinguished - BHPian
 
Thad E Ginathom's Avatar
 
Join Date: Jun 2007
Location: Chennai
Posts: 7,839
Thanked: 7,209 Times
Default

Quote:
Originally Posted by watashi75 View Post
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?
Thad E Ginathom is offline  
Old 26th September 2009, 09:31   #614
BHPian
 
Tempelhof's Avatar
 
Join Date: Oct 2007
Location: Bangalore
Posts: 450
Thanked: 123 Times
Default

Quote:
Originally Posted by Thad E Ginathom View Post
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 is offline  
Old 26th September 2009, 10:49   #615
BHPian
 
Tempelhof's Avatar
 
Join Date: Oct 2007
Location: Bangalore
Posts: 450
Thanked: 123 Times
Default

Quote:
Originally Posted by psp62in View Post
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
Tempelhof is offline  
Closed Thread


Thread Tools Search this Thread
Search this Thread:

Advanced Search


Similar Threads
Thread Thread Starter Forum Replies Last Post
Goodyear's Self Inflating Tyres carboy Tyre & Alloy wheel Section 1 26th September 2012 00:15
Inflating a tire with liquid fire Takumi-san Technical Stuff 6 28th September 2010 13:47
Nitrogen in car tyres ac 427 Technical Stuff 2 26th April 2007 15:46
Nitrogen filling in car tyres sn48001 Tyre & Alloy wheel Section 1 5th January 2007 14:47


All times are GMT +5.5. The time now is 21:18.

Copyright ©2000 - 2017, Team-BHP.com
Proudly powered by E2E Networks