Inflation?

[sweaty]

I read recently that race car tires (open wheel) are inflated with nitrogen instead of air.
If so why?

[Fueler]

Nitrogen is an inert gas, and typically contains less moisture than does compressed air. That means that as it is heated (i.e. from temperature build-up on the track) it expands at a more consistent rate, thereby keeping the effects of increasing pressure more consistent. That makes for predictable results when a crew chief tries to change the handling of the car through air pressure adjustments.

[Indycarjunkie]

That is true. Its a matter of physics. The air that we breathe is full of different elements, which will all expand differently as they are heated. By inflating a tire with pure nitrogen the expansion of the gas (and therefore increased 'air' pressure) is much more predictable and eleminates an unknown variable in the car setup.

[Snakepit Dave]

There you go with all your "science". The first Indy Car team to experiment with different gasses was a German team in the 30's. The car known as the Hindenberg Special was written off in a fiery incident in Lakehurst, New Jersey (Oh the Humanity!) Hydrogen inflation was banned from the sport. Later a team experimented with Helium, which caused most of the team to talk funny and sadly, one of their cars floated away when someone let go of the string. That really left only Methane, Oxygen or Nitrogen. Early experiments with Methane left a bad taste in everyone's mouth. Oxygen was too basic (50 cents at Village Pantry) so Nitrogen was selected because it's:

Cool
You have to order it
Comes in a Green Metal Cylinder

So yes, Victoria, there is a little bit of Nitrogen in every Indy Car tire.

Next week: Why Argon and Neon were very bad choices as inflation gasses.

[sweaty]

:d

[nascarnation]

Next week: Why Argon and Neon were very bad choices as inflation gasses.

wow this is like hs chemistry review
"Argon is 2.5 times as soluble in water as nitrogen"
and neon I'm guessing is a small molecule that would leak bigtime?

[speedgeek]

I read recently that race car tires (open wheel) are inflated with nitrogen instead of air.
If so why?

Enough of the science mumbo-jumbo.

The reason they use nitrogen is because that's the gas that comes in the big bottles!

(fueler is spot on, of course. The Nitro is used to run the air jacks, impact wrenches, everything.)

[Radny]

I heard somewhere that you should put nitrogen in your car tires to improve gas mileage. I think there was even a place here in town offering it. Does that make sense, or just a waste of $?

[Spike]

Keep in mind the air we breathe is mostly nitrogen. About 79% nitrogen, in fact, so there isn't much difference between filling a tire with "air" and filling it nitrogen. Also, basically all gases behave in the same manner with regard to pressure and temperature. So the other gases that make up the air we breathe expand at the same rate.





Check out "Boyle's Law" for a more complete explanation but in simple terms in an enclosed space, the pressure of Nitrogen increases linearly with temperature. If the temperature increases by 1%, the pressure goes up by 1%. The same is true for the blend of Nitrogen, Oxygen and other gases we call "air". The same is even true for the gas known as water vapor.

Don't forget when the techs at the track mount a tire they do it out in the open so (not in a nitrogen-filled, enclosed chamber) so there's already a fair volume of "air" in the tire. Where water is a slight concern is if it goes into the tire as a liquid and then undergoes a phase shift (changes from a liquid to a gas). In that instance the volume of the water changes quite a bit. Not really much of a concern as most commercial air compressors have dryers on the output to remove moisture.

The main reason you'll see teams use nitrogen to inflate tires is because that's what's in the cylinders they have on their pit wagons and back at the trailers. The main use for those cylinders powering their air tools which benefit from a dry supply. High pressure bottled nitrogen is dry (and cheap) and widely available.

[Spike]

I heard somewhere that you should put nitrogen in your car tires to improve gas mileage....

Um, no.

[irloyal]

I don't think any of the teams use all nitrogen anymore. Firestone mounts all the tires and they use air for this. The air dryers Firestone use are the key. The air is now so dry that it has virtually no change in density based on temperature. It is the moisture in the air that has the radical effect on volume with temperature changes.

Now it is true that the teams do have nitrogen in their pits. Typically the teams use the nitrogen for touch-up on pressure, this ensures they do not introduce any moisture.

[Indycarjunkie]

Check out "Boyle's Law" for a more complete explanation but in simple terms in an enclosed space, the pressure of Nitrogen increases linearly with temperature. If the temperature increases by 1%, the pressure goes up by 1%. The same is true for the blend of Nitrogen, Oxygen and other gases we call "air". The same is even true for the gas known as water vapor.

You are quite right and now that I think about it, Fueler's explanation is far more accurate than mine. Chemestry is fun! This sorta makes me want to drop some sodium down the (someone else's) sink drain.

[Jim Wilke]

There you go with all your "science". The first Indy Car team to experiment with different gasses was a German team in the 30's. The car known as the Hindenberg Special was written off in a fiery incident in Lakehurst, New Jersey (Oh the Humanity!) Hydrogen inflation was banned from the sport. Later a team experimented with Helium, which caused most of the team to talk funny and sadly, one of their cars floated away when someone let go of the string. That really left only Methane, Oxygen or Nitrogen. Early experiments with Methane left a bad taste in everyone's mouth. Oxygen was too basic (50 cents at Village Pantry) so Nitrogen was selected because it's:

Cool
You have to order it
Comes in a Green Metal Cylinder

So yes, Victoria, there is a little bit of Nitrogen in every Indy Car tire.

Next week: Why Argon and Neon were very bad choices as inflation gasses.

Neon would make the tires glow? Is that a bad thing?

[brickyard1911]

I heard somewhere that you should put nitrogen in your car tires to improve gas mileage. I think there was even a place here in town offering it. Does that make sense, or just a waste of $?

I have heard that also but I don't think the theory behind it is to improve gas mileage. I believe it is to reduce pressure fluctuation based on temperature. Obviously, if your pressure remains closer to the optimal setting your gas mileage should be steady. With that said, I think I'll check my pressure. Its only 40 degress colder that it was... what 4 days ago. Ahhhhh, Northeast Ohio.... What's not to love!

[Jakester]

Nah, the real reason was to add a revenue stream to the gas station and/or to companies like Parker-Hannifin . First they started charging for air, then they went to the crappy little compressors in a box that had no line drier. Now, they want to charge even more for filling your tires with nitrogen, which is no better than the free dry air of long ago.

Take a look at these 'benefits'

Consistent inflation pressure over longer periods
- Nitrogen permeates through the tire at a rate of 35% slower that oxygen (air)
- Under inflated tires flex and build up heat, breaking down the rubber over time
- 60% of blowouts are caused by under inflation
- Consistent inflation improves tread life
- Vehicle handling is improved
Maybe nitrogen does permeate slower than oxygen, but Air is 78% nitrogen, so one would only recognize 22% of the 35% improvement (is that 7%?). None of the rest of the above advantages have anything to do with nitrogen, merely inflation.

Longer Tire Life
- Nitrogen is a dry gas which disperses heat more rapidly resulting in cooler running tires. This preserves the integrity of the rubber, belts, and bead
- This inert gas also significantly slows the chemical aging process associated with oxygen and moisture (air)
Air is also a dry gas when run through even an inexpensive line drier. Heat dispersion, again air is 78% nitrogen. Tread life is gonna be shorter than the physical life of the tire, unless you introduce massive amounts of water.

Improved fuel efficiency
- Passenger cars realize 2-3 miles per gallon gains (4% on average*)
- Trucks realize gains of 2+%
At 4% fuel efficiency enhancement, the savings are significant to the car owner
- At 4% on a vehicle with 20 mpg rating, this saves approximately 2.5 gallons per week based on 40 miles per day @ $1.90 per gallon that adds up to $228 savings per year
EH? At the same tire pressures with air and nitrogen, exactly what mythical science reduces rolling resistance, friction, stiction, hysteresis or any other factor to increase mileage by 4%. However, it is correct that tires inflated to proper pressures will result in better mileage than with tires that are underinflated.