Nitrogen in run flats
#27
06-02-2011, 09:58 AM
Same thing also usually happens on audio forums with discussions on the merits of expensive cables (but much, much worse in that case).
#28
06-02-2011, 10:09 AM
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i think its a good discussion. we are all civil here :D its like the discussion of how to break in your engine, either keep the rpms low, or flog the hell out of it :D
#29
06-02-2011, 10:12 AM
#31
06-02-2011, 12:58 PM
Just out of curiosity, since I am certainly NOT an expert on transport phenomena, do you know roughly what that difference in permeability is?
Curious because by increasing the concentration of nitrogen in the tire vs the outside air, wouldn't you be increasing the permeation rate of N2 out of the tire?
Assuming 49.7 psia in the tire and 14.7 psia atm., 79% N2 in air:
With air you are at a N2 partial pressure of 39.3 inside the tire, 11.6 outside the tire, so a difference of 27.7
With 100% N2, you are at a n2 partial pressure of 49.7 psi inside, 11.6 outside, so a difference of 38.1, or about 37% higher than air. So I would assume the permeability of O2 vs N2 in rubber has to be quite a bit higher?
Also interesting on the CR study. Would be good to know if they were using dry air as a comparison. Funny tire manufacturers did not think nitrogen was necessary. Not sure a 1.3 psi difference in a year is significant enough for me to worry about anyway
Curious because by increasing the concentration of nitrogen in the tire vs the outside air, wouldn't you be increasing the permeation rate of N2 out of the tire?
Assuming 49.7 psia in the tire and 14.7 psia atm., 79% N2 in air:
With air you are at a N2 partial pressure of 39.3 inside the tire, 11.6 outside the tire, so a difference of 27.7
With 100% N2, you are at a n2 partial pressure of 49.7 psi inside, 11.6 outside, so a difference of 38.1, or about 37% higher than air. So I would assume the permeability of O2 vs N2 in rubber has to be quite a bit higher?
Also interesting on the CR study. Would be good to know if they were using dry air as a comparison. Funny tire manufacturers did not think nitrogen was necessary. Not sure a 1.3 psi difference in a year is significant enough for me to worry about anyway
Personally if it's not too expensive I will switch to nitrogen because I don't see any down side.
CN
#32
06-02-2011, 01:48 PM
#33
06-04-2011, 05:35 AM
4th Gear
Unless you're getting your tires filled in a vacuum, there's no way you're going to have 100% nitrogen in them. Even a flat tire will still have a substantial amount of regular air in it.
And as many have mentioned, the air we breathe is already 78% nitrogen.
I think that any place that charges for nitrogen is ripping off their customers unless they have some kind of a vacuum they put the tires in before filling them with nitrogen.
But if it's free, like it seems to be for a few of you, go for it. I wouldn't pay anything for it though.
And as many have mentioned, the air we breathe is already 78% nitrogen.
I think that any place that charges for nitrogen is ripping off their customers unless they have some kind of a vacuum they put the tires in before filling them with nitrogen.
But if it's free, like it seems to be for a few of you, go for it. I wouldn't pay anything for it though.
#34
06-06-2011, 05:49 AM
I will be mounting the new NE Eng. 19" Countryman wheels soon as the tires come in Tues/Wed. of this week. I have the original 17" tunnel spoke (anthracite) wheels with the run flat all seasons straight from the build, for sale next week if any one is interested..Approx 4650 current miles, excellent shape..View them in my gallery...PM me
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