Nitrogen filled Race Tires?
08-22-2006, 04:46 PM
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Originally Posted by Voodoo_S2K,Aug 22 2006, 11:35 AM
Gimmick. You will not notice any difference in tire pressures between the two.
08-22-2006, 07:26 PM
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Originally Posted by smracer31,Aug 22 2006, 05:46 PM
wrong. Nitrogen is more stable and keeps the air at a more stable level. as the tires heat up nitrogen is less prone to expanding the tires and keeps it more stable which keeps your tire pressure down. the more heat in a tire the higher the tire pressure will be. when you use nitrogen you can get more heat in the tire and keep it at a lower psi.
08-22-2006, 07:29 PM
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Chemistry is by far my worst science, but I think the nitrogen thing is a total myth, so here's my attempt to disprove it:
PV=nRT
P is pressure - we'll come back to that, since that's what we're trying to calculate the difference for, depending on the gas.
V Volume basically is fixed by the tire's reinforcements, which make it largely inelastic.
n is the number of moles of the gas. At a given starting point of pressure and volume, this number should be the same for any ideal gas, be it nitrogen, oxygen, chlorine, hydrogen, etc.
R is the universal gas constant. It's a constant - end of story.
T Temperature rises as you drive.
Since everything else is fixed except for pressure, the pressure is the only thing that changes as temperature rises and it will increase at the same rate relative to temperature regardless of which if these gases you're using.
-------------------------
The idea is to have a DRY gas source. If you have moisture in the tire, the water will convert back and forth between liquid and gasious forms as the temp goes up and down and that WILL create much greater pressure changes than you will see with a simple dry gas.
I think people just use nitrogen for filling the tires because it's cheap and readily available. But I can't see any reason why it's going to perform any better than argon or any other gas you take from a purified source.
Ok, someone who actually stayed awake in Chemistry can come in and correct me now.
PV=nRT
P is pressure - we'll come back to that, since that's what we're trying to calculate the difference for, depending on the gas.
V Volume basically is fixed by the tire's reinforcements, which make it largely inelastic.
n is the number of moles of the gas. At a given starting point of pressure and volume, this number should be the same for any ideal gas, be it nitrogen, oxygen, chlorine, hydrogen, etc.
R is the universal gas constant. It's a constant - end of story.
T Temperature rises as you drive.
Since everything else is fixed except for pressure, the pressure is the only thing that changes as temperature rises and it will increase at the same rate relative to temperature regardless of which if these gases you're using.
-------------------------
The idea is to have a DRY gas source. If you have moisture in the tire, the water will convert back and forth between liquid and gasious forms as the temp goes up and down and that WILL create much greater pressure changes than you will see with a simple dry gas.
I think people just use nitrogen for filling the tires because it's cheap and readily available. But I can't see any reason why it's going to perform any better than argon or any other gas you take from a purified source.
Ok, someone who actually stayed awake in Chemistry can come in and correct me now.
08-22-2006, 07:33 PM
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The small amount of moisture that you find in normal compressed air is some small as to have virtual no effect on pressure. Definitely not what you could measure what your average tire pressure gauge. If you feel that you must use dry air, just use scuba air. Its a lot cheaper than Nitrogen.
08-22-2006, 07:54 PM
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Originally Posted by Voodoo_S2K,Aug 22 2006, 07:33 PM
The small amount of moisture that you find in normal compressed air is some small as to have virtual no effect on pressure. Definitely not what you could measure what your average tire pressure gauge. If you feel that you must use dry air, just use scuba air. Its a lot cheaper than Nitrogen.
and i suppose you have evidence to back up your claims, cause i sure do
08-22-2006, 07:56 PM
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Originally Posted by smracer31,Aug 22 2006, 05:46 PM
wrong. Nitrogen is more stable and keeps the air at a more stable level. as the tires heat up nitrogen is less prone to expanding the tires and keeps it more stable which keeps your tire pressure down. the more heat in a tire the higher the tire pressure will be. when you use nitrogen you can get more heat in the tire and keep it at a lower psi.
Here is were your wrong. The reason to use Nitrogen to keep the tire pressure more consistent (less pressure increase). With less tire pressure change you will be able to dial in the optimum tire pressure for a longer period of time.
I will give you some real world data (data taken from thunderhill raceway). On my car, with toyo RA1s and my optimum tire pressure is 35 psi. My right front tire takes the most beating (most heat and PSI growth). When I use my little portable Snap-on air compressor I fill that tire to 26 PSI before I go on the track. When I come off after a 30 min session it had grown to 35 psi. The last time I used nitrogen (I purged the tires before use) I started with the same pressure and came off at 34 PSI. After starting at 27 PSI the next time out I came off the track at 35 PSI (both time the average core tire temp was 190 deg)
For a general track day or club racer my personal opinion is it
08-22-2006, 08:04 PM
#19
Originally Posted by Voodoo_S2K,Aug 22 2006, 08:33 PM
The small amount of moisture that you find in normal compressed air is some small as to have virtual no effect on pressure. Definitely not what you could measure what your average tire pressure gauge. If you feel that you must use dry air, just use scuba air. Its a lot cheaper than Nitrogen.
08-22-2006, 08:52 PM
#20
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Originally Posted by The Reverend,Aug 22 2006, 11:29 PM
Chemistry is by far my worst science, but I think the nitrogen thing is a total myth, so here's my attempt to disprove it:
PV=nRT
P is pressure - we'll come back to that, since that's what we're trying to calculate the difference for, depending on the gas.
V Volume basically is fixed by the tire's reinforcements, which make it largely inelastic.
n is the number of moles of the gas. At a given starting point of pressure and volume, this number should be the same for any ideal gas, be it nitrogen, oxygen, chlorine, hydrogen, etc.
R is the universal gas constant. It's a constant - end of story.
T Temperature rises as you drive.
Since everything else is fixed except for pressure, the pressure is the only thing that changes as temperature rises and it will increase at the same rate relative to temperature regardless of which if these gases you're using.
-------------------------
The idea is to have a DRY gas source. If you have moisture in the tire, the water will convert back and forth between liquid and gasious forms as the temp goes up and down and that WILL create much greater pressure changes than you will see with a simple dry gas.
I think people just use nitrogen for filling the tires because it's cheap and readily available. But I can't see any reason why it's going to perform any better than argon or any other gas you take from a purified source.
Ok, someone who actually stayed awake in Chemistry can come in and correct me now.
PV=nRT
P is pressure - we'll come back to that, since that's what we're trying to calculate the difference for, depending on the gas.
V Volume basically is fixed by the tire's reinforcements, which make it largely inelastic.
n is the number of moles of the gas. At a given starting point of pressure and volume, this number should be the same for any ideal gas, be it nitrogen, oxygen, chlorine, hydrogen, etc.
R is the universal gas constant. It's a constant - end of story.
T Temperature rises as you drive.
Since everything else is fixed except for pressure, the pressure is the only thing that changes as temperature rises and it will increase at the same rate relative to temperature regardless of which if these gases you're using.
-------------------------
The idea is to have a DRY gas source. If you have moisture in the tire, the water will convert back and forth between liquid and gasious forms as the temp goes up and down and that WILL create much greater pressure changes than you will see with a simple dry gas.
I think people just use nitrogen for filling the tires because it's cheap and readily available. But I can't see any reason why it's going to perform any better than argon or any other gas you take from a purified source.
Ok, someone who actually stayed awake in Chemistry can come in and correct me now.
