[R Kelly]

Re: (SilverS60RNYC)

Quote, originally posted by SilverS60RNYC »

nitrogen does expand with heat....

not much though... the real expansion is because of water vapor present in compressed air. Water vapor is not present in nitrogen. Why airplanes, race cars, and cars in germany run on it.

Quote, originally posted by SilverS60RNYC »

your pressure will increase the same amount for a given increase in temp. whether you use air or "pure" nitrogen (IIRC, you go from 78.5% nitrogen in regular air to about 88-93% with the special filling)

see above for why this isn't true.

 

[SilverS60RNYC]

Re: ("R" Kelly)

Quote, originally posted by "R" Kelly »

not much though... the real expansion is because of water vapor present in compressed air. Water vapor is not present in nitrogen. Why airplanes, race cars, and cars in germany run on it. see above for why this isn't true.

water vapor behaves as an ideal gas so P V = n R T still applies. even up to over 300PSI. the pressure increase is due to an increase in kinetic energy of the molecules. water vapor/nitrogen/oxygen all react basically the same once the water becomes a vapor. the phase change has already occured.

the small amount of water in normal air, is already in vapor form. heating will not cause water vapor to deviate drastically, especially under normal car conditions (<200F inside the tire) from the ideal gas law.

not saying that there's anything wrong with nitrogen filled tires. but the reality is, its mainly a gimmick. if you get it for free, its no big deal, but if you're paying a premium and thinking that its vastly superior to regular air.....

 

[Helmut Ranff]

Re: (SilverS60RNYC)

Nitrogen molecules migrate 3 to 4 times more slowly than oxygen, so tires stay properly inflated longer. There are other benefits. Nitrogen retains less heat than oxygen and therefore allows tires to run cooler.

Nitrogen is dry and clean and will not combine chemically with other materials but air contains water (especially gas station air) and the oxygen and water can cause corrosion in the wheel.

Tour de France bicyclists fill their tires with it. So do NASCAR, Indy and F1 , airplanes, long distance truckers, fire departments and the military.

I would not say it's gimmick

 

[Mash]

Re: (Helmut Ranff)

I am running 34 psi in the front and 36psi in the rear. Regular air. I run 19" H5's all the way around with Goodyear Eagle F1's. I have tried higher and lower psi (either too hard or too soft) Car handles great. PSI goes up to 39psi front and 42-44psi rear after 10-15 minutes of highway driving. I wonder if the tire companies that are telling us to "fill up" to a certain psi are telling us to fill up the tire when warm.?"????????

 

[SilverS60RNYC]

Re: (Helmut Ranff)

Quote, originally posted by Helmut Ranff »

Nitrogen molecules migrate 3 to 4 times more slowly than oxygen, so tires stay properly inflated longer. There are other benefits. Nitrogen retains less heat than oxygen and therefore allows tires to run cooler. I would not say it's gimmick

sigh...

02 has a molecular weight thats higher than n2.that would lend it to diffuse more slowly than n2. molecular diameter is close, 0.36nm vs 0.38nm

since air is ~80% n2 to begin with, only 20% of the air will diffuse faster, about 0.1% faster. mind you the nitrogen they fill with is only about 90-95% pure. so its even less than that. and thats basing it on theoretical molecular diameter vs the actual molecular weight and diffusion rates.

specific heat:
Specific heat 1.04 J/gK (nitrogen)
Specific heat 1.005 J/gK (air)

the rubber of the tire holds much more heat than any gas could. it is a solid afterall

nitrogen actually absorbs slightly more energy before increasing in temperature

you are correct about corrosion in the wheel, but thats not really an issue. have you ever seen a wheel rust out from the inside, even a steel wheel?

plus, when the tire is mounted, its filled with a volume of regular air equal to the inside volume of the tire at atmospheric pressure. unless you purge the tire, its not going to make a huge difference.

airplanes are another story. their tires are subject to temps that would cause any water vapor to condense and freeze. -50F at altitude. the phase change from gas to liquid to solid would make a difference in air volume. also, airplane tires are inflated to >200psi. much easier to do with a 1500psi canister of nitrogen than a pump. same story with road bike tires, those are often at 100psi+
i used to use nitrogen to fill mountain bike shocks, but that was because hitting 300-600psi with an airpump was almost impossible.
long haul truckers use tires that are retreaded over many hundred thousand miles. here, your nitrogen will slow down tire carcass breakdown. not a factor with a car tire that has 1/10 to 1/100th the life expectancy.

you cant overcome the laws of physics and chemistry with marketing unfortunately

 

[Mash]

Re: (SilverS60RNYC)

WOW. Above post is DEEP. Right on! http://********************/smile/emthup.gif

 

[Helmut Ranff]

Re: (SilverS60RNYC)

I guess all F1, Indy, Nascar and other racing teams are not as smart as you or the marketing just got to them

 

[martynunya]

Re: (Helmut Ranff)

Perhaps it is more due to the inert properties of N2, reduces the risk of fire/explosion?

 

[Pelle Schultz]

Re: (Helmut Ranff)

Quote, originally posted by Helmut Ranff »

I guess all F1, Indy, Nascar and other racing teams are not as smart as you or the marketing just got to them

Ok, the scientist in me can be restrained no longer. What SilverS60RNYC has stated is essentially correct. For the 'casual' driver--and by that I mean anyone who's not racing professionally--anyone who claims they can feel the difference between 78% nitrogen (normal atmosphere) and the 90-odd percent they'd get in a nitrogen fill is talking out their a$$.

In a high-performance apllication like racing--in which tires will be pushed to their limits and maintained there for extended periods--or over a long, long period of time (e.g. the long-haul truckers example), one might find a relatively slight but still statistically significant difference.

As for anyone who claims they can feel a difference under normal driving, do a case-control study and get back to me. No one's a$$ is that sensitive.

 

[Helmut Ranff]

Re: (Pelle Schultz)

I am only talking about racing

 

[R Kelly]

Re: (Pelle Schultz)

Quote, originally posted by Pelle Schultz »

In a high-performance apllication like racing--in which tires will be pushed to their limits and maintained there for extended periods--or over a long, long period of time (e.g. the long-haul truckers example), one might find a relatively slight but still statistically significant difference.

Hmmm, ok I'm glad the scientist in you came out, but you sure missed some important pieces of data.

I'M IN FREAKING GERMANY, AND DRIVE AT ABOVE 130 MPH FOR EXTENDED PERIODS OF TIME. YOU MAY HAVE HEARD OF THE AUTOBAHN.

I REGULARLY GO TO 12.9 MILE NORDSCHLEIFE AT NURBURGRING, ONE OF THE MOST DEMANDING TRACKS IN THE WORLD ON TIRES.

Jim Lill reccomended Nitrogen to me before I went to Ring for the first time. He uses it, along with all racing teams, so I know it is not a marketing gimmick. And at only 2 euros per tire for life of tire, I don't know that they even make money on it here to call it a marketing gimmick.

Regardless, last summer I ran Nitrogen, and after 8,000 miles (inlcuding autobahn and 14 laps on the ring), I only lost .05 bar (.7 psi) in two tires, NONE on the others. That means essentially ZERO pressure loss over some serious driving. Don't have scientific data to explain why that is true, but someone had mentioned that I would see less pressure loss over time, and they were correct.

Again, if you can explain why it is a waste of time for all racing teams and performance sedans running at 100+ mph on the autobahn to run nitrogen, please do. I'm sure they'll listen.

Me, I'm gonna keep running it.

Quote, originally posted by Pelle Schultz »

As for anyone who claims they can feel a difference under normal driving, do a case-control study and get back to me. No one's a$$ is that sensitive.

PLEASE show me ANYWHERE where I said I could feel a difference. NO ONE has ever said anything about feeling a difference. And my ass is insulted, it is very sensitive.

 

[Pedestrian_A]

42psi all around on 18" PS2.

I never run lower than 40psi on 17" and over because the tire guy said low tire pressure will incease the chance of bending rims.

 

[Pelle Schultz]

Re: ("R" Kelly)

Quote, originally posted by "R" Kelly »

I'M IN FREAKING GERMANY, AND DRIVE AT ABOVE 130 MPH FOR EXTENDED PERIODS OF TIME. YOU MAY HAVE HEARD OF THE AUTOBAHN. I REGULARLY GO TO 12.9 MILE NORDSCHLEIFE AT NURBURGRING, ONE OF THE MOST DEMANDING TRACKS IN THE WORLD ON TIRES.

Kelly...you're running under the high-performance conditions that most of us only dream of and our cars will never see. Like I said, you might indeed see a difference.

Quote, originally posted by "R"Kelly »

Regardless, last summer I ran Nitrogen, and after 8,000 miles (inlcuding autobahn and 14 laps on the ring), I only lost .05 bar (.7 psi) in two tires, NONE on the others. That means essentially ZERO pressure loss over some serious driving. Don't have scientific data to explain why that is true, but someone had mentioned that I would see less pressure loss over time, and they were correct.

You'd have to repeat that AT LEAST two more times and do the same thing with 'normal' air three times under as identical conditions as possible, then calculate the standard errors and show me the readings to make me a believer.

Quote, originally posted by "R"Kelly »

Again, if you can explain why it is a waste of time for all racing teams and performance sedans running at 100+ mph on the autobahn to run nitrogen, please do.

I believe my statement was that you would see a slight but nevertheless significant difference under those conditions. In typical street use--which likely accounts for 99.9% of the mileage accrued by street-legal cars worldwide--you won't see a difference. You still have nothing to lose by filling with nitrogen--but if you're paying extra $$$ to do it and you never drive over 100 mph for extended periods or track your car, you're pissing $$$ away.

Quote, originally posted by "R"Kelly »

PLEASE show me ANYWHERE where I said I could feel a difference. NO ONE has ever said anything about feeling a difference. And my ass is insulted, it is very sensitive.

Kelly...don't ask, don't tell!

 

[JARMO]

Re: Proper Tire Inflation for 18" vs 17" ("R" Kelly)

I use 2.8bar (40.6PSI) at the fronts
and
2.5bar (36.3PSI) at the back

and wear at the fronts is dead even on the entire surface

rears look like they wear evenly but I don't care...they always go to the front when I put new tires at the back and again this set at the front now, is worn perfectly at the end. I just love these Rosso's http://********************/smile/emlove.gif

 

[Helmut Ranff]

Re: Proper Tire Inflation for 18" vs 17" (JARMO)

I use 38.5 all around and rotate every 3000 which is more than most I suspect

 

[superstein61]

Re: Proper Tire Inflation for 18" vs 17" ("R" Kelly)

Quote, originally posted by "R" Kelly »

Most people on here always say run 36 psi. I wonder if underinflation is why so many people with 18" rims get damage from potholes?

YES - the two blowouts I have had on my 18" rims have been running 35psi. One when I didn't know any better, the other on the way home from the Dealer's service dept who "adjusted" the pressure for me when the car was in for service (I didn't ask for this). I had much better success at 39psi

 

[MrTippy]

Re: (SilverS60RNYC)

Quote, originally posted by SilverS60RNYC »

the small amount of water in normal air, is already in vapor form. heating will not cause water vapor to deviate drastically, especially under normal car conditions (<200F inside the tire) from the ideal gas law.

Actually the water in the tire may not be vapor at all times, it is temperature (and pressure dependent) and at cooler temps it may be liquid or even frozen. Hence, water inside a tire will produce wider pressure swings than a tire that is filled with dry gases, i.e. the nitrogen being sold for tires. Nitrogen in itself is not a "wundercompound," it is as close to being a free raw material as a company could find. That is why they are making such a big push to dry and sell it, at very high markup, to the consumer. The operative word for all of this is DRY.