Nitrogen doesn't leak ...

996 4S 2002 done 8,500 KM Front Tyres 225/40 ZR 18 Rear Tyres 295/30 ZR 18 We all know that tyres filled with Nitrogen will maintain their correct pressure for longer, because Nitrogen doesn't leak through the tyre's structure??? dono how true this is ??? Pirelli dealer workshop filled the tyres with Nitrogen 60 days back, the guage now reads 27psi front and 36psi rear. Please advise:- 1- Temp in Dubai is 30 deg. it says in the manual front should be 36psi and rear 44psi, is this true for Dubai's weather? 2- If it is true, should they fill the same pressure with Nitrogen? Knowing that i didn't check the tyres pressure after the job is done. 3- Does it mean that i have leak in the tyres or 60 days is more than enough knowing that i drive her twice a week and the rest of the time i give her a chance to rest I filled the tyres yesterday with air NOT Nitrogen to the required, front 36 and rear 44. Results: Yesterday Steering wheel minimum vibration all the time. Today vibration is vanished Thanks in advance <img src="graemlins/a_smil17.gif" border="0" alt="[blabla]" />

As far as I know, the advantage of using nitrogen over regular air for tires is the reduced moisture/water content of nitrogen. As a result, there is almost no variation in tire pressure between cold and hot tires with a nitrogen fill. I've never heard anything about the "less leakage" issue.

Now this is one topic i'd love to read answers for! Fadz, FYI: Nitrogen holds tyre pressures for longer. A 20% tyre pressure drop reduces tyre life by 15% and pushes fuel bills up by 3%. Over the last few years the filling of tyres with nitrogen has increased dramatically in popularity in countries such as Germany and Italy where almost every tyre shop and garage is equipped with a source of nitrogen - for example: heavy gas cylinders. Nitrogen has for many years been an accepted gas medium for filling tyres of aircraft and F1 racing cars. Nitrogen is used for safety reasons and to ensure that tyres are always at constant pressure. Go back and fill nitro and change your number plates to 'C4BOMB' !!! <img src="graemlins/roflmao.gif" border="0" alt="[hiha]" /> Waz

The advantages of nitrogen are the ones described by Jack. Also is more inert than oxygen so it might preserve the rubber and valve better. But the main point is that nitrogen is the cheapest industrial pure gas so you can have a dry non-flammable gas at a relatively low cost. Nitrogen bottles are less than US$15.- each. To Fadz I will say that tire pressures recommendations are independent of the external temperatures unless you drive at 0 degrees C in the morning and then at 30 in the afternoon (not very likely).

Waz, that really isn't logical. I'm not saying that garages in Europe don't do this; I believe you. I'm just saying that tires filled with nitrogen will leak at about the same rate as tires filled with air. But bottled nitrogen IS dry and I believe that is why it is used. Air is 78% nitrogen, 21% oxygen, 1% argon with trace amounts of other elements and compounds. The oxygen and nitrogen are both diatomic molecules with similar molecular masses; 32 for diatomic oxygen (O2) and 28 for diatomic nitrogen.(N2). Diffusion rates of gases are inversely proportional to the square root of the density of the gas. So nitrogen would leak a bit faster than oxygen. But the difference is very small. So you can see that a tire filled with nitrogen isn't going to leak slower than a tire filled with air. Also, the change in pressure caused by temperature will be about the same; all gases obey the ideal gas law. So a nitrogen filled tire will increase in pressure as the gas temperature rises just like an air filled tire. My question is why would you care if the gas had water vapor?

Air generated by a compression always has some water in it. The water molecules will heat and expand, causing the tire pressure to increase significantly between cold and hot temps (8-12psi), especially with extreme use as on a track or at high speed on the autobahn. Nitrogen is dry, assuming you get your tank from a good dealer who purges the tank properly before filling it. Because there is no water vapor in it, the hot pressure does not increase nearly as much, thus as others have pointed out, the hot pressures will not dramatically change from cold (2-4 psi). For street use, it doesn't matter that much. You can use air, set the tires at your preferred or the manufacturers recommended cold pressure and forget about it. For racing or track use, a nitrogen tire will be more consistent between cold and hot conditions because it pressure change is much less. Karl

You know guys, I felt myself i am attending a chemistry session(201) in the science lecture hall in college, say in 1986, anyway i appreciate the knowledge you offered, but the real question is? Are the tyres pressure right wether Nitrogen or Air? Front 36 Rear 44 Thanks again

Fadz, here's lecture 2 for you: PV=nRT.. no matter what the gaz inside, pressure is pressure wael

I posted this question on another list I belong to with people that know quite a bit about chemistry and the anwsers were: Yes nitrogen tires achieve less temperature because even though gases expand the same with heat (PV=nRT), the especific heat of nitrogen is lower (by20%)than air (20%N-80%O) and therefore air needs lees heat to achieve a higher temperature. Yes nitrogen inflated tires leak less gas with time because more oxygen is lost with oxidation-increased heat and also the rubber compound of the tires are more permeable to oxigen. Yes nitrogen inflated tires are safer because nitrogen is not inflamable so doesn�t contribute to combustion, this is why its used in airplanes who's tire temps get quite high. But in applied to ordinary street cars these diferences are insignificant to make a big enough difference.

Fadz,to answer ur first quistion on how much pressure to put. I'm not far off from u in Bahrain and I usually put 32 front and 40 rear. Works for me

[quote]Originally posted by Fadz: <strong>You know guys, I felt myself i am attending a chemistry session(201) in the science lecture hall in college, say in 1986, anyway i appreciate the knowledge you offered, but the real question is? Are the tyres pressure right wether Nitrogen or Air? Front 36 Rear 44 Thanks again</strong><hr></blockquote> Actually your pressures are way, way off. Lower the fronts by abour 3 or 4 psi and the rears by about 8 and you will have a much better riding and handling car.

[quote]Originally posted by Carlos from Spain: <strong>...the especific heat of nitrogen is lower (by20%)than air (20%N-80%O)...</strong><hr></blockquote> Actually, air is something like 78% nitrogen, 21% oxygen. Still curious why nitrogen is more stable for inflating tires at the track, but I'm satisfied that "bottled nitrogen gas is drier" may be correct. Curt

Because nitrogen doesn�t heat up as much therfore expands less therefore maintains the set tire pressures better.

You bubbas are wayy two funny. Now ol JimBob iz pert good at makin dis stuff up but yall is way beterer dan me. Did yall kome up wit dis stuf by yerselves or did u werk tagether ta do dis. I specailly likey da parts bout specifical heets an how da notrigen (at aboot a billionth of da wait of da tire)wood makin any differnce at awl. Best hope dat no won evr does sumtin crazee like aktually mesure a tire tempertur wit a pyromometer cuz den they'all knwin yall makin dis stuff up outa da air. yall crakin ol JimmyBob up.

I have always wondered how much truth there is to the nitrogen claim - so I spent 2 hours reading articles on the net - search "nitrogen in tires." In an interview I read the guy being quoted states that he puts in in his garden tractor, bicycle, and wheel barrow - then I realized he sells the stuff. Then I saw claims that tires would last 26% longer - which make no sense to me - then I found out it was 18 wheel truck tires that are retreaded and expected to last 100k plus. In the space shuttle, certain aircraft, race cars, and other special applications it makes sense. My opinion is the same as Carlos. One of the web sites informed prospective purchasers of the nitrogen equipment how they could make more money from ordinary customers by upselling nitrogen when tires on a street car are replaced. Did you know that due to NFL regulations a football must have 16 psi. So if the team inflates the ball at sea level and then plays in Denver they must adjust the pressure before the game. Now, there is a good use for nitrogen - just a joke. I am going to put helium in my street car - less unsprung weight. Jeff

[quote]<strong>I am going to put helium in my street car - less unsprung weight. </strong><hr></blockquote> Not true!!! Well, I am sure there is a specific gravity difference between helium and air but the idea that helium will just make everything lighter doesn't work. Helium must be accelerated up or down and around and around just as air does. To prove this consider a blimp. Have you ever seen a fast blimp? S.

[quote]Originally posted by 02-targa911: <strong>Fadz,to answer ur first quistion on how much pressure to put. I'm not far off from u in Bahrain and I usually put 32 front and 40 rear. Works for me </strong><hr></blockquote> What you mentioned is reasonable as long as the size of the tyres are front 225/40 and rear 295/30??? Do you have the same tyres size? One more thing since you are in Bahrain, do you think i can find a clean 964 cabrio out there? Thanks

[quote]Originally posted by Greg Fishman: <strong> Actually your pressures are way, way off. Lower the fronts by abour 3 or 4 psi and the rears by about 8 and you will have a much better riding and handling car.</strong><hr></blockquote> Greg, do you think the extra pressure in tyres made the vibration of the steering wheel? Thanks

[quote]Originally posted by Fadz: <strong> Greg, do you think the extra pressure in tyres made the vibration of the steering wheel? Thanks</strong><hr></blockquote> My guess is the tires had a slight flat spot from sitting. It usually goes away after driving for a distance, and getting the tires warm, also depends on how long the car has sat. Pirelli's seem to be worse for this than other brands I have had

[quote]Originally posted by Karl S: <strong>Air generated by a compression always has some water in it. The water molecules will heat and expand, causing the tire pressure to increase significantly between cold and hot temps (8-12psi), especially with extreme use as on a track or at high speed on the autobahn. Nitrogen is dry, assuming you get your tank from a good dealer who purges the tank properly before filling it. Because there is no water vapor in it, the hot pressure does not increase nearly as much, thus as others have pointed out, the hot pressures will not dramatically change from cold (2-4 psi). Karl</strong><hr></blockquote> Others here have dealt with the theortical so I will only relate my personal experience. I started carrying N so I could adjust my Penske shocks. I believe that is how the whole N use in tires got started - you had a ready source of gas to add a little pressure to tire. Once I started doing this I thought it would be cool to run all N in the tires are that is what the Indycar guys were doing. Now admittedly I had no way to evacuate the tire completely. I just let all the air out and refilled with N, so there was a small amount of air with a trivial amount of moisture in it. My experience was quite different than quoted above. The pressure rise was quite similar when using plain ol' air. I think others on this thread have explained way quite well. Race tires seem to seep a little air when they are unused and I didn't notice any change in that behavior. In asking around about this, I was told (by the tire guy for the Ganassi team) that the real benefit is that because N is dry they get a more consistant pressure rise when they use from humid conditions vs. drier ones. Since they change pressures regularly by as little as half a pound, they feel there is a benefit. The benefit is in the repeatability of making the car handle a certain way with certain settings. In closing, I don't see any benefit at all in running N in a street car. With that said, it certainly won't hurt anything either.