Damn my high school only education! My buddy runs something other than 'regular air' because he says it does not raise the air pressure as much when the heat of the tire raises..... what is it? I know you guys know this one.

 

nitrogen... why not post this in the wheel and tire forum

 

Nitrogen. It's used simply because it's convienient, and doesn't have water vapor in it. That's what's happening, the water vapor changes the pressure, while nitrogen won't change as much.
[edit] beat me to it!

 

 

And just incase some people are thinking this DO NOT USE HELIUM. Even though it's an inert gas it actually dries out rubber robbing the rubber of the oils/petrolium products that keep it supple and soft.

Someone on our cycling team did this way back when I was in college in 1990. He was coming around a corner when his tire blew. We found out later that the atoms for helium are so small that they seep out of the rubber inner tube of your tire and carry along with it the oils that make rubber soft. This guy's tire was brittle like paper.

Nitrogen is better since it is a larger atom.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by CivicSiRacer &raquo;</TD></TR><TR><TD CLASS="quote">

Nitrogen is better since it is a larger atom.</TD></TR></TABLE>

Actually, Nitrogen gas are molecules of two Nitrogen atoms and thus are even bigger than the inert and singular Helium atoms composing Helium gas.

 

dry air is much like nitrogen for your tires. like someone mentioned, its the moisture in the tire air that affects pressuers, after all air is mostly nitrogen in the first place. Pirelli race tires at ALMS uses dry air because an compressed air dryer is cheaper than cylinders of nitrogen on the track.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Johnny Mac &raquo;</TD></TR><TR><TD CLASS="quote">

Actually, Nitrogen gas are molecules of two Nitrogen atoms and thus are even bigger than the inert and singular Helium atoms composing Helium gas. </TD></TR></TABLE>

Whoops that's what I meant College is so 16 years ago

 

I don't know if this is a really dumb question, but here it is anyways. Does a wheel and tire weigh more with regular air or nitrogen. The wheel and tire is being filled are identical.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by george34 &raquo;</TD></TR><TR><TD CLASS="quote"> I don't know if this is a really dumb question, but here it is anyways. Does a wheel and tire weigh more with regular air or nitrogen. The wheel and tire is being filled are identical.</TD></TR></TABLE>

I'm not bored enough to do the actual calculations, but as said above: "regular air" is about 80% nitrogen. So with pure nitrogen, your wheel & tire would be slightly lighter. But the difference would be so small you'd never see it on any scale you're likely to find.

 

Actually i believe nitrogen is heavier than oxygen so it would be slightly heavier. But we're talkin an unmeasureable amount here.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Furyof4 &raquo;</TD></TR><TR><TD CLASS="quote">Actually i believe nitrogen is heavier than oxygen so it would be slightly heavier. But we're talkin an unmeasureable amount here.</TD></TR></TABLE>

Nitrogen is element #7, Oxygen is #8. But my guess is that the removal of atmospheric moisture would make a much bigger weight difference, anyway.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by bender &raquo;</TD></TR><TR><TD CLASS="quote">

Nitrogen is element #7, Oxygen is #8. But my guess is that the removal of atmospheric moisture would make a much bigger weight difference, anyway.</TD></TR></TABLE>

woops I just checked, your right.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by vietnameeh &raquo;</TD></TR><TR><TD CLASS="quote">nitrogen... why not post this in the wheel and tire forum</TD></TR></TABLE>

Because road racers know this stuff.... not some dude looking for 19's on his hatch.

Plus, road racers are pretty geeky. I have guys giving atomic weights by the end of the thread.

 

Helium !

so your car is lighter !!!

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by CivicSiRacer &raquo;</TD></TR><TR><TD CLASS="quote">DO NOT USE HELIUM</TD></TR></TABLE>
<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by CivicSiRacer &raquo;</TD></TR><TR><TD CLASS="quote">This guy's tire was brittle like paper.</TD></TR></TABLE>

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by civic_iv &raquo;</TD></TR><TR><TD CLASS="quote"> </TD></TR></TABLE>
hydrogen??

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by george34 &raquo;</TD></TR><TR><TD CLASS="quote"> I don't know if this is a really dumb question, but here it is anyways. Does a wheel and tire weigh more with regular air or nitrogen. The wheel and tire is being filled are identical.</TD></TR></TABLE>

According to my calculations on a 225-50-14 tire using rough numbers for the actual air volume. I assumed the volume was pi(10.7^2 - 7^2)*(8 inches),which assumes the tire construction is approx. .5 inch thick. Remember, round numbers only for a first approximation.

So, the volume is about 1645 in^3 or 27 liters. Assuming the tire pressure is 2 atm (gage) or 3 atm absolute, temperature is 300 Kelvin, gas constant R = .0821 atm - liter/ mole - Kelvin and using the ideal gas law PV = nRT,

The number of moles of gas is 3.3 moles.

Molecular weight of dry air = 28.97 grams/mole
Molecular weight of nitrogen = 28.02 g/m

Thus, the mass of air in my hypothetical tire is 96 grams and for nitrogen, the mass is 92 grams. The nitrogen would reduce the weight compared with dry air by 4 grams per tire, or .009 lbs.

Of course, air pumped from a compressor would have a large moisture content so that the actual weight difference between actual air and dry nitrogen would be much higher. In addition, the moisture content in the tire is the large unknown and if the amount were large, then once the tire got up to temperature and some of this liquid water evaporates, the overall tire pressure would increase to some difficult to predict value. And we all know how important the hot tire pressures are for performance even at the club level. At the pro level, it is even more important.

By using nitrogen, this unknown moisture content isn't an issue. This is why pro teams use nitrogen or other "dry" gases so they can better predict the necessary cold pressures when setting up the car for each track session. Once the tire heats up, the hot pressures should be very close to what the engineers predicted.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Johnny Mac &raquo;</TD></TR><TR><TD CLASS="quote">According to my calculations on a 225-50-14 tire using rough numbers for the actual air volume. I assumed the volume was pi(10.7^2 - 7^2)*(8 inches),which assumes the tire construction is approx. .5 inch thick. Remember, round numbers only for a first approximation.

So, the volume is about 1645 in^3 or 27 liters. Assuming the tire pressure is 2 atm (gage) or 3 atm absolute, temperature is 300 Kelvin, gas constant R = .0821 atm - liter/ mole - Kelvin and using the ideal gas law PV = nRT,

The number of moles of gas is 3.3 moles.

Molecular weight of dry air = 28.97 grams/mole
Molecular weight of nitrogen = 28.02 g/m

Thus, the mass of air in my hypothetical tire is 96 grams and for nitrogen, the mass is 92 grams. The nitrogen would reduce the weight compared with dry air by 4 grams per tire, or .009 lbs.

Of course, air pumped from a compressor would have a large moisture content so that the actual weight difference between actual air and dry nitrogen would be much higher. In addition, the moisture content in the tire is the large unknown and if the amount were large, then once the tire got up to temperature and some of this liquid water evaporates, the overall tire pressure would increase to some difficult to predict value. And we all know how important the hot tire pressures are for performance even at the club level. At the pro level, it is even more important.

By using nitrogen, this unknown moisture content isn't an issue. This is why pro teams use nitrogen or other "dry" gases so they can better predict the necessary cold pressures when setting up the car for each track session. Once the tire heats up, the hot pressures should be very close to what the engineers predicted.</TD></TR></TABLE>

You got too much time on your hands, Mac. Maybe its time to get a job...

 

Sounds to me like he just knows his stuff

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Johnny Mac &raquo;</TD></TR><TR><TD CLASS="quote">

According to my calculations on a 225-50-14 tire using rough numbers for the actual air volume. I assumed the volume was pi(10.7^2 - 7^2)*(8 inches),which assumes the tire construction is approx. .5 inch thick. Remember, round numbers only for a first approximation.

So, the volume is about 1645 in^3 or 27 liters. Assuming the tire pressure is 2 atm (gage) or 3 atm absolute, temperature is 300 Kelvin, gas constant R = .0821 atm - liter/ mole - Kelvin and using the ideal gas law PV = nRT,

The number of moles of gas is 3.3 moles.

Molecular weight of dry air = 28.97 grams/mole
Molecular weight of nitrogen = 28.02 g/m

Thus, the mass of air in my hypothetical tire is 96 grams and for nitrogen, the mass is 92 grams. The nitrogen would reduce the weight compared with dry air by 4 grams per tire, or .009 lbs.

Of course, air pumped from a compressor would have a large moisture content so that the actual weight difference between actual air and dry nitrogen would be much higher. In addition, the moisture content in the tire is the large unknown and if the amount were large, then once the tire got up to temperature and some of this liquid water evaporates, the overall tire pressure would increase to some difficult to predict value. And we all know how important the hot tire pressures are for performance even at the club level. At the pro level, it is even more important.

By using nitrogen, this unknown moisture content isn't an issue. This is why pro teams use nitrogen or other "dry" gases so they can better predict the necessary cold pressures when setting up the car for each track session. Once the tire heats up, the hot pressures should be very close to what the engineers predicted.</TD></TR></TABLE>

HAHA. Good one! I was just going over this with my wife yesterday when I was helping her study for her Chemistry exam.

 

Don't car collectors also use nitrogen in their tires to prevent corrosion on the very rare wheels that are on their very rare cars?

 

Nitrogen works pretty good. It does not loose as much air (even thou my work says it never changes for a year, haha - not true) as normal compressed air (even with an inline dryer as most shops have) and doesn't go up and down as much with temperature changes. The only thing is, if want to change air pressures at the track its much easier to use a portable air compressor to add air than to haul around a nitrogen station/tank with you. The biggest thing is make sure you purge your tire correctly when adding nitrogen.

Also, nitrogen keeps your tires cooler