Nitrogen in tires - Page 2 - PeachParts Mercedes-Benz Forum

aersloat · #16 08-04-2006, 05:06 PM

Nitrogen is very inert and heats up less. It also will have a less detrimental effect on your rubber than O2, but I would see this as a minor benefit/factor. I believe the biggest benefit is the decreased tendency to loose tire pressure, which of course results in an overall increase in MPG. They do purge (or at least Costco does) when they fill.

Hatterasguy · #17 08-04-2006, 08:39 PM

Costco filled the tires in my dads truck with N2 when he bought new ones. No mileage difference, but inflation pressure stayed the same.

I'll continue to use regular air because its 80% N2 already. Someone let the marketing department lose again.

ConnClark · #18 08-04-2006, 09:58 PM

Nitrogen is ever so slightly better than air because it has less water and co2 than air. Nitrogen and oxygen are diatomic molecules. H2O an CO2 are tri atomic molecules. Diatomic molecules have a higher specific heat ratio than tri atomic ones. This gives them more bounce because more heat energy added to them goes into moving the molecules than it does spinning them. You can prove this experimentally by filling a basket ball with CO2 and helium(which is monotomic and doesn't spin) and see which one bounces better.

here is a link to a more scientific experiment with math http://www.physics.uoguelph.ca/~detong/phys3510/specheat.pdf

(Source http://www.engineeringtoolbox.com/specific-heat-ratio-d_608.html )
Specific heat ratio of

Helium 1.66
dry air 1.4
oxygen 1.4
nitrogen 1.4
Co2 1.3

Since air is 78% nitrogen and 21% oxygen we are at 99%. How much does the 1 % cost you? Probably about 1 to 2% less bounce. Which translates into 1 to 2% more rolling friction.

aersloat · #19 08-05-2006, 02:22 AM

Quote:

Originally Posted by Hatterasguy

I'll continue to use regular air because its 80% N2 already. Someone let the marketing department lose again.

At least at Costco the Nitrogen is the default and there is no added charge-- so it really isn't a choice you have to make.

t walgamuth · #20 08-05-2006, 11:06 AM

i could see it might help a little but it would seem to me it would be small enough it would be very difficult to measure.

tom w

andmoon · #21 08-05-2006, 11:18 AM

Less variation in pressure due to temp change...and the added ugliness of green valve stem caps...

Jeremy5848 · #22 08-05-2006, 12:06 PM

Google <"urban legend" nitrogen tires> and you will learn why commercial aircraft and NASCAR racers use compressed nitrogen to "air up" their tires. You will also learn why it isn't worth the bother or expense to use it for car tires. If nitrogen is conveniently available to you for free, go ahead -- it won't hurt. If it means you must go out of your way to get it, or pay for it, you're better off washing the car or checking the oil more frequently, or sending me a check every month --

-- then we both feel good (I also accept PayPal).

Jeremy

dmorrison · #23 08-05-2006, 02:17 PM

The nitrogen does, and has a reason for being used. The tires runs cooler causing less heat damage, longer life and less pressure buildup. The nitrogen remains cooler so the tire remains cooler.

Airliners tires can be filled ONLY with nitrogen. Back in 1986 a Mexicana 727 main landing gear tire was filled with regular air. The jet had a long taxi and was heavy. It was also at Mexico city Which is at 6000'MSL and gets very hot. This produced a very long takoff roll which heats up the tires. Hot brakes and air in the tire was a factor that caused a main tire to explode just after takeoff, while retracted in the landing gear wheel well. The structural damage was major and the aircraft crashed and all 167 on board were killed.

So putting nitrogen in tires has a reason and purpose. Is it necassary for auto tires? As pointed out its free at Costco. Pay extra? I would not.

Hope this ends this discussion.

Dave

Jeremy5848 · #24 08-05-2006, 02:32 PM

"Flight 940 took off from Mexico City at 08:40 for a flight to Puerto Vallarta, Mazatlan and Los Angeles. The left main gear brake was overheated during the take-off run and (when the aircraft had reached FL310) caused a tyre on the left hand main gear to explode. Fuel and hydraulic lines were ruptured and electrical cables severed resulting in a cabin decompression. An emergency was declared, but spilt fuel ignited and caused a massive fire on board. Control was lost and the aircraft crashed into a mountain in the Sierra Madre, at an elevation of 9000 feet. It was found that the tire had been serviced with air rather than nitrogen. The air, under high temperature and pressure, resulted in a chemical reaction with the tire itself. This led to a chemical explosion of the tire."

http://aviation-safety.net/database/record.php?id=19860331-1&lang=en

dunl · #25 08-05-2006, 02:40 PM

So don't fill your Mercedes tires with air if you don't want them to explode?

79300sdtd · #26 08-05-2006, 09:56 PM

I am sure that the molecular weight of N2 is slightly less thatn that of a molecule of air. One molecule of N2 weighs 4.65*10^-23 grams one molecule of air weighs 4.80*10^-23 grams. So air weighs 1.24*10^-24 more than N2 so for every 6.022*10^23 molecules you are saving 1.24 grams in weight, there is another possible scientific reason why. if some one can find the exact ammount of volume in their tire i can give them how much weight they can save over all.. my guess is going to be maybe 1-2 lbs of weight MAYBE.

#27 08-05-2006, 10:01 PM

Quote:

Originally Posted by 79300sdtd

my guess is going to be maybe 1-2 lbs of weight MAYBE.

More like 1-2oz.

#28 08-05-2006, 10:10 PM

Quote:

Originally Posted by 79300sdtd

I am sure that the molecular weight of N2 is slightly less thatn that of a molecule of air. One molecule of N2 weighs 4.65*10^-23 grams one molecule of air weighs 4.80*10^-23 grams. So air weighs 1.24*10^-24 more than N2 so for every 6.022*10^23 molecules you are saving 1.24 grams in weight, there is another possible scientific reason why. if some one can find the exact ammount of volume in their tire i can give them how much weight they can save over all.. my guess is going to be maybe 1-2 lbs of weight MAYBE.

Well sorta, there's no such thing as a "molecule of air." Air is a mixture of N2, O2, usually H2O, and some trace elements. What you are trying to do is calculate the density of the N2 and air. If you look up the density of both at standard conditions, multiply by the volume of the tire, and multiply by about 3 (to account for about 30 psig pressure) you will get the answer.

ConnClark · #29 08-07-2006, 12:19 PM

Pure O2 is lighter than pure N2. They originally used pure O2 in the Apollo 1 capsule to save weight. After the fatal fire I think they switched to pure N2 and made the crew breath out of their suits until orbit was reached.

I wonder how much of an improvement a tire filled with neon would do? Helium would be better but would leak out quicker.

Jeremy5848 · #30 08-07-2006, 01:41 PM

The difference in weight between a tire full of N2 and one with O2 is so small that nothing anyone here has could measure it.

NASA spacecraft were originally designed to use pure oxygen at 5 psi. This was simpler than a "two gas" system (meaning, oxygen plus nitrogen, as in "air"). It also meant that the crew could do EVAs without any pre-breathing (as is now done on ISS) since they were going from pure O2 in the spacecraft to the same thing in their suits. A one-gas system at low pressure also means that the spacecraft leaks less.

After the Apollo 1 fire, they switched to a mixture of gases in the spacecraft. Carefully crafted from nitrogen and oxygen (mostly), this mixture is commonly known as "air" and is what the Shuttle and the ISS use.

Interestingly, from the very beginning, the Soviets designed their spacecraft to use air. In the world of engineering tradeoffs, they "won," since their design is what is used today. Not that it did them any good.

NASA experimented with helium in the tires of the SR-71 Blackbird (they were on a weight-saving drive) but, as you have indicated, it leaked out too fast to be useful. They gave up and used dry nitrogen.

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