Nitrogen for tire inflation

[Erik Freitag]

My local Costco is advertising their use of nitrogen for automobile tire
inflation. They say nitrogen is a dry, inert gas used to inflate airplane
tires, off-road truck tires, military vehicle tires and race car tires for
improved performance.

Apparently, the oxygen in compressed air is bad for tires, and I assume,
tubes.

So, does topeak or zefal make a reasonably priced, frame-mounted nitrogen
generator?

[MikeYankee]

Another reason nitrogen is used in some aircraft tires (jets) is that it will
not sustain combustion. There is a very significant amount of oxygen in a
large air-filled tire at ~200 psi.


Mike Yankee

(Address is munged to thwart spammers.
To reply, delete everything after "com".)

[MikeYankee]

Another reason nitrogen is used in some aircraft tires (jets) is that it will
not sustain combustion. There is a very significant amount of oxygen in a
large air-filled tire at ~200 psi.


Mike Yankee

(Address is munged to thwart spammers.
To reply, delete everything after "com".)

[[email protected]]

On Fri, 15 Oct 2004 10:18:53 -0700, Erik Freitag
> wrote:

>My local Costco is advertising their use of nitrogen for automobile tire
>inflation. They say nitrogen is a dry, inert gas used to inflate airplane
>tires, off-road truck tires, military vehicle tires and race car tires for
>improved performance.
>
>Apparently, the oxygen in compressed air is bad for tires, and I assume,
>tubes.
>
>So, does topeak or zefal make a reasonably priced, frame-mounted nitrogen
>generator?

Dear Erik,

Probably not, but years ago bottles of compressed nitrogen
were carried by Tour riders:

http://groups.google.com/groups?hl=en&lr=&selm=10j0976e68s38b2%40corp.supernews.com

or

http://tinyurl.com/66hj2

If you browse the thread, you'll see suggestions that the
nitrogen oozes out (sorry, the right word escapes me)
through the rubber of the inner tube more slowly than CO2.

Carl Fogel

[[email protected]]

On Fri, 15 Oct 2004 10:18:53 -0700, Erik Freitag
> wrote:

>My local Costco is advertising their use of nitrogen for automobile tire
>inflation. They say nitrogen is a dry, inert gas used to inflate airplane
>tires, off-road truck tires, military vehicle tires and race car tires for
>improved performance.
>
>Apparently, the oxygen in compressed air is bad for tires, and I assume,
>tubes.
>
>So, does topeak or zefal make a reasonably priced, frame-mounted nitrogen
>generator?

Dear Erik,

Probably not, but years ago bottles of compressed nitrogen
were carried by Tour riders:

http://groups.google.com/groups?hl=en&lr=&selm=10j0976e68s38b2%40corp.supernews.com

or

http://tinyurl.com/66hj2

If you browse the thread, you'll see suggestions that the
nitrogen oozes out (sorry, the right word escapes me)
through the rubber of the inner tube more slowly than CO2.

Carl Fogel

[Doug Huffman]

Amount? BS I'll bet you can't tell us how many moles. In any case there
is still more N2 (80%) than O2 (20%) in any volume of 'air' at any pressure.


"MikeYankee" > wrote in message
...
> Another reason nitrogen is used in some aircraft tires (jets) is that it
> will
> not sustain combustion. There is a very significant amount of oxygen in
> a
> large air-filled tire at ~200 psi.
>
>
> Mike Yankee
>
> (Address is munged to thwart spammers.
> To reply, delete everything after "com".)

[Doug Huffman]

Amount? BS I'll bet you can't tell us how many moles. In any case there
is still more N2 (80%) than O2 (20%) in any volume of 'air' at any pressure.


"MikeYankee" > wrote in message
...
> Another reason nitrogen is used in some aircraft tires (jets) is that it
> will
> not sustain combustion. There is a very significant amount of oxygen in
> a
> large air-filled tire at ~200 psi.
>
>
> Mike Yankee
>
> (Address is munged to thwart spammers.
> To reply, delete everything after "com".)

[Leo Lichtman]

I am convinced it is a gimmick. I picked up the brochure at the Costco tire
shop, and studied it. The main "advantage" of nitrogen is that the molecule
is slightly heavier than oxygen, so it seeps out of the tire more slowly.
This, supposedly, results in less tendency toward underinflation. And, of
course, we all know that underinflated tires don't wear properly, and cause
loss of gas mileage. If you watch your tire pressures, then there is no
advantage. If you start out with a nitrogen-filled tire, and watch your
tire pressures, you will eventually replace most of the nitrogen with air.

However, if you start out with air in your tires, and the oxygen leaks
faster than the nitrogen, as you keep topping up, you will gradually
increase the concentration of nitrogen in your tires.

IMO, Costco is spending money on nitrogen in order to improve tire sales.

[Leo Lichtman]

I am convinced it is a gimmick. I picked up the brochure at the Costco tire
shop, and studied it. The main "advantage" of nitrogen is that the molecule
is slightly heavier than oxygen, so it seeps out of the tire more slowly.
This, supposedly, results in less tendency toward underinflation. And, of
course, we all know that underinflated tires don't wear properly, and cause
loss of gas mileage. If you watch your tire pressures, then there is no
advantage. If you start out with a nitrogen-filled tire, and watch your
tire pressures, you will eventually replace most of the nitrogen with air.

However, if you start out with air in your tires, and the oxygen leaks
faster than the nitrogen, as you keep topping up, you will gradually
increase the concentration of nitrogen in your tires.

IMO, Costco is spending money on nitrogen in order to improve tire sales.

[Bill Lloyd]

Nitrogen certainly seeps out more slowly than CO2. Fill your tire with
CO2 and it's flat within a day or two.

Nitrogen is nice and inert, and it's also like 73% of the content of
normal air. I think Oxygen is around 16%. Someone else can check my
figures ;-)

On 2004-10-15 12:45:07 -0700, said:

> On Fri, 15 Oct 2004 10:18:53 -0700, Erik Freitag
> > wrote:
>
>> My local Costco is advertising their use of nitrogen for automobile tire
>> inflation. They say nitrogen is a dry, inert gas used to inflate airplane
>> tires, off-road truck tires, military vehicle tires and race car tires for
>> improved performance.
>>
>> Apparently, the oxygen in compressed air is bad for tires, and I assume,
>> tubes.
>>
>> So, does topeak or zefal make a reasonably priced, frame-mounted nitrogen
>> generator?
>
> Dear Erik,
>
> Probably not, but years ago bottles of compressed nitrogen
> were carried by Tour riders:
>
> http://groups.google.com/groups?hl=en&lr=&selm=10j0976e68s38b2%40corp.supernews.com

or

http://tinyurl.com/66hj2

If
>
>
> or
>
> http://tinyurl.com/66hj2
>
> If you browse the thread, you'll see suggestions that the
> nitrogen oozes out (sorry, the right word escapes me)
> through the rubber of the inner tube more slowly than CO2.
>
> Carl Fogel

[Bill Lloyd]

Nitrogen certainly seeps out more slowly than CO2. Fill your tire with
CO2 and it's flat within a day or two.

Nitrogen is nice and inert, and it's also like 73% of the content of
normal air. I think Oxygen is around 16%. Someone else can check my
figures ;-)

On 2004-10-15 12:45:07 -0700, said:

> On Fri, 15 Oct 2004 10:18:53 -0700, Erik Freitag
> > wrote:
>
>> My local Costco is advertising their use of nitrogen for automobile tire
>> inflation. They say nitrogen is a dry, inert gas used to inflate airplane
>> tires, off-road truck tires, military vehicle tires and race car tires for
>> improved performance.
>>
>> Apparently, the oxygen in compressed air is bad for tires, and I assume,
>> tubes.
>>
>> So, does topeak or zefal make a reasonably priced, frame-mounted nitrogen
>> generator?
>
> Dear Erik,
>
> Probably not, but years ago bottles of compressed nitrogen
> were carried by Tour riders:
>
> http://groups.google.com/groups?hl=en&lr=&selm=10j0976e68s38b2%40corp.supernews.com

or

http://tinyurl.com/66hj2

If
>
>
> or
>
> http://tinyurl.com/66hj2
>
> If you browse the thread, you'll see suggestions that the
> nitrogen oozes out (sorry, the right word escapes me)
> through the rubber of the inner tube more slowly than CO2.
>
> Carl Fogel

[Werehatrack]

On Fri, 15 Oct 2004 10:18:53 -0700, Erik Freitag
> wrote:

>My local Costco is advertising their use of nitrogen for automobile tire
>inflation. They say nitrogen is a dry, inert gas used to inflate airplane
>tires, off-road truck tires, military vehicle tires and race car tires for
>improved performance.

The FAA only requires that nitrogen be used for tire inflation on
*braked wheels*, with topping off with air permitted as long as O2
content does not exceed 5% in the tire. This requirement was imposed
due to tire explosions resulting from release of combustible gases
inside the tire secondary to overheating during landings. An
automotive tire that reached the kinds of temps experienced in those
circumstances would fail anyway. A bike tire is extremely unlikely to
get anywhere near those temps without a failure as well.

>Apparently, the oxygen in compressed air is bad for tires, and I assume,
>tubes.

This is silly. There's O2 on the outside of *all* tires. Billions of
undamaged air-inflated tires also belie this assertion.

>So, does topeak or zefal make a reasonably priced, frame-mounted nitrogen
>generator?

No. Nor will they.

If you want to fill your tires with nitrogen, a high-pressure bottle
of it can be had from any welding gas supplier. Do not expect
sympathy from your SO for the back strain or smashed toes that you may
acquire in bringing it home, and don't expect it to pass muster as a
living room decor item. Make sure that you have a place to secure it
against falling over; if you break the service valve off of a bottle
of nitrogen, you have just created a cast iron rocket engine that
produces enough thrust to go right through a cinder block wall or a
car's body sheet metal. Buy a *good* pressure regulator to use with
it, as the fill pressure is typically around 3000 psi. Alternately, a
tank of liquid nitrogen (DO NOT store this in any enclosed
unventilated space!) is not overly expensive[1] and provides the
opportunity for instantly creating condensation clouds on demand in
moist climates, a useful thing at this time of year.




[1] for certain values of the phrase "not overly expensive", anyway.


--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

[Werehatrack]

On Fri, 15 Oct 2004 10:18:53 -0700, Erik Freitag
> wrote:

>My local Costco is advertising their use of nitrogen for automobile tire
>inflation. They say nitrogen is a dry, inert gas used to inflate airplane
>tires, off-road truck tires, military vehicle tires and race car tires for
>improved performance.

The FAA only requires that nitrogen be used for tire inflation on
*braked wheels*, with topping off with air permitted as long as O2
content does not exceed 5% in the tire. This requirement was imposed
due to tire explosions resulting from release of combustible gases
inside the tire secondary to overheating during landings. An
automotive tire that reached the kinds of temps experienced in those
circumstances would fail anyway. A bike tire is extremely unlikely to
get anywhere near those temps without a failure as well.

>Apparently, the oxygen in compressed air is bad for tires, and I assume,
>tubes.

This is silly. There's O2 on the outside of *all* tires. Billions of
undamaged air-inflated tires also belie this assertion.

>So, does topeak or zefal make a reasonably priced, frame-mounted nitrogen
>generator?

No. Nor will they.

If you want to fill your tires with nitrogen, a high-pressure bottle
of it can be had from any welding gas supplier. Do not expect
sympathy from your SO for the back strain or smashed toes that you may
acquire in bringing it home, and don't expect it to pass muster as a
living room decor item. Make sure that you have a place to secure it
against falling over; if you break the service valve off of a bottle
of nitrogen, you have just created a cast iron rocket engine that
produces enough thrust to go right through a cinder block wall or a
car's body sheet metal. Buy a *good* pressure regulator to use with
it, as the fill pressure is typically around 3000 psi. Alternately, a
tank of liquid nitrogen (DO NOT store this in any enclosed
unventilated space!) is not overly expensive[1] and provides the
opportunity for instantly creating condensation clouds on demand in
moist climates, a useful thing at this time of year.




[1] for certain values of the phrase "not overly expensive", anyway.


--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

[Erik Freitag]

On Sat, 16 Oct 2004 00:03:35 +0000, Werehatrack wrote:

> This is silly. There's O2 on the outside of *all* tires. Billions of
> undamaged air-inflated tires also belie this assertion.

They didn't specify that you had to have a nitrogen-only environment only
on the inside. Maybe there's a coating or something for the outside.

> Do not expect sympathy from your SO

Amen, bruddah. Not for this or any bike-related issue.

>if you break the service valve off of a
> bottle of nitrogen, you have just created a cast iron rocket engine

OK, now we're getting somewhere. What's the smallest (lightest) size I can
get? This sounds like just the thing for getting me past the junction on
Mt. Diablo. Forget putting it in the tires, I want it for thrust.

[Erik Freitag]

On Sat, 16 Oct 2004 00:03:35 +0000, Werehatrack wrote:

> This is silly. There's O2 on the outside of *all* tires. Billions of
> undamaged air-inflated tires also belie this assertion.

They didn't specify that you had to have a nitrogen-only environment only
on the inside. Maybe there's a coating or something for the outside.

> Do not expect sympathy from your SO

Amen, bruddah. Not for this or any bike-related issue.

>if you break the service valve off of a
> bottle of nitrogen, you have just created a cast iron rocket engine

OK, now we're getting somewhere. What's the smallest (lightest) size I can
get? This sounds like just the thing for getting me past the junction on
Mt. Diablo. Forget putting it in the tires, I want it for thrust.

[Werehatrack]

On Fri, 15 Oct 2004 17:09:34 -0700, Erik Freitag
> wrote:

>On Sat, 16 Oct 2004 00:03:35 +0000, Werehatrack wrote:
>
>> This is silly. There's O2 on the outside of *all* tires. Billions of
>> undamaged air-inflated tires also belie this assertion.
>
>They didn't specify that you had to have a nitrogen-only environment only
>on the inside. Maybe there's a coating or something for the outside.

The inside is where the low-permeability layer is found, if one is
used. Whatever the inner surface may be, you can be sure that it's a
compound formulated to *not* degrade in the presence of compressed
air.

>>if you break the service valve off of a
>> bottle of nitrogen, you have just created a cast iron rocket engine
>
>OK, now we're getting somewhere. What's the smallest (lightest) size I can
>get? This sounds like just the thing for getting me past the junction on
>Mt. Diablo. Forget putting it in the tires, I want it for thrust.

Neither cost-effective, trivially controllable, or practical, I'm
afraid. Rockets on bikes are for cartoon coyotes; they regenerate in
a few frames.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

[Werehatrack]

On Fri, 15 Oct 2004 17:09:34 -0700, Erik Freitag
> wrote:

>On Sat, 16 Oct 2004 00:03:35 +0000, Werehatrack wrote:
>
>> This is silly. There's O2 on the outside of *all* tires. Billions of
>> undamaged air-inflated tires also belie this assertion.
>
>They didn't specify that you had to have a nitrogen-only environment only
>on the inside. Maybe there's a coating or something for the outside.

The inside is where the low-permeability layer is found, if one is
used. Whatever the inner surface may be, you can be sure that it's a
compound formulated to *not* degrade in the presence of compressed
air.

>>if you break the service valve off of a
>> bottle of nitrogen, you have just created a cast iron rocket engine
>
>OK, now we're getting somewhere. What's the smallest (lightest) size I can
>get? This sounds like just the thing for getting me past the junction on
>Mt. Diablo. Forget putting it in the tires, I want it for thrust.

Neither cost-effective, trivially controllable, or practical, I'm
afraid. Rockets on bikes are for cartoon coyotes; they regenerate in
a few frames.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

[Leo Lichtman]

"Werehatrack"(clip)This requirement was imposed due to tire explosions
resulting from release of combustible gases inside the tire secondary to
overheating during landings. (clip)
^^^^^^^^^^^^
Are you sure about this? Oxygen is not a combustible gas. If an air-filled
tire overheated for any reason, and exploded, it would release a cloud of
the same gas that was already present on the outside of the tire--AIR.

Thought experiment: bury an air-inflated tire in lighted charcoal. The
tire will heat up, catch fire, and explode. The charcoal will scatter, and
glow slightly brighter for a fraction of a second, due to the blowing of air
from within the pile. No further explosion would occur.

[Leo Lichtman]

"Werehatrack"(clip)This requirement was imposed due to tire explosions
resulting from release of combustible gases inside the tire secondary to
overheating during landings. (clip)
^^^^^^^^^^^^
Are you sure about this? Oxygen is not a combustible gas. If an air-filled
tire overheated for any reason, and exploded, it would release a cloud of
the same gas that was already present on the outside of the tire--AIR.

Thought experiment: bury an air-inflated tire in lighted charcoal. The
tire will heat up, catch fire, and explode. The charcoal will scatter, and
glow slightly brighter for a fraction of a second, due to the blowing of air
from within the pile. No further explosion would occur.

[Marcus Coles]

Werehatrack wrote:

> On Fri, 15 Oct 2004 17:09:34 -0700, Erik Freitag
> > wrote:
>
>
>>On Sat, 16 Oct 2004 00:03:35 +0000, Werehatrack wrote:
>>
>>
>>>This is silly. There's O2 on the outside of *all* tires. Billions of
>>>undamaged air-inflated tires also belie this assertion.
>>
>>They didn't specify that you had to have a nitrogen-only environment only
>>on the inside. Maybe there's a coating or something for the outside.
>
>
> The inside is where the low-permeability layer is found, if one is
> used. Whatever the inner surface may be, you can be sure that it's a
> compound formulated to *not* degrade in the presence of compressed
> air.
>
>
>>>if you break the service valve off of a
>>>bottle of nitrogen, you have just created a cast iron rocket engine
>>
>>OK, now we're getting somewhere. What's the smallest (lightest) size I can
>>get? This sounds like just the thing for getting me past the junction on
>>Mt. Diablo. Forget putting it in the tires, I want it for thrust.
>
>
> Neither cost-effective, trivially controllable, or practical, I'm
> afraid. Rockets on bikes are for cartoon coyotes; they regenerate in
> a few frames.

Don't spoil all the fun!

http://www.dself.dsl.pipex.com/MUSEUM/TRANSPORT/rocketbicycle/rocketbicycle.htm

Marcus Coles

[Marcus Coles]

Werehatrack wrote:

> On Fri, 15 Oct 2004 17:09:34 -0700, Erik Freitag
> > wrote:
>
>
>>On Sat, 16 Oct 2004 00:03:35 +0000, Werehatrack wrote:
>>
>>
>>>This is silly. There's O2 on the outside of *all* tires. Billions of
>>>undamaged air-inflated tires also belie this assertion.
>>
>>They didn't specify that you had to have a nitrogen-only environment only
>>on the inside. Maybe there's a coating or something for the outside.
>
>
> The inside is where the low-permeability layer is found, if one is
> used. Whatever the inner surface may be, you can be sure that it's a
> compound formulated to *not* degrade in the presence of compressed
> air.
>
>
>>>if you break the service valve off of a
>>>bottle of nitrogen, you have just created a cast iron rocket engine
>>
>>OK, now we're getting somewhere. What's the smallest (lightest) size I can
>>get? This sounds like just the thing for getting me past the junction on
>>Mt. Diablo. Forget putting it in the tires, I want it for thrust.
>
>
> Neither cost-effective, trivially controllable, or practical, I'm
> afraid. Rockets on bikes are for cartoon coyotes; they regenerate in
> a few frames.

Don't spoil all the fun!

http://www.dself.dsl.pipex.com/MUSEUM/TRANSPORT/rocketbicycle/rocketbicycle.htm

Marcus Coles

[Threeducks]

Leo Lichtman wrote:
> I am convinced it is a gimmick. I picked up the brochure at the Costco tire
> shop, and studied it. The main "advantage" of nitrogen is that the molecule
> is slightly heavier than oxygen, so it seeps out of the tire more slowly.

No, the molecular weight of N2 is 28 g/mol while the MW of O2 is 32 g/mol.

[Threeducks]

Leo Lichtman wrote:
> I am convinced it is a gimmick. I picked up the brochure at the Costco tire
> shop, and studied it. The main "advantage" of nitrogen is that the molecule
> is slightly heavier than oxygen, so it seeps out of the tire more slowly.

No, the molecular weight of N2 is 28 g/mol while the MW of O2 is 32 g/mol.

[Werehatrack]

On Sat, 16 Oct 2004 02:05:39 GMT, "Leo Lichtman"
> wrote:

>
>"Werehatrack"(clip)This requirement was imposed due to tire explosions
>resulting from release of combustible gases inside the tire secondary to
>overheating during landings. (clip)
>^^^^^^^^^^^^
>Are you sure about this?

Yes.

Here's the Boeing statement:

http://www.boeing.com/commercial/aeromagazine/aero_05/textonly/m03txt.html

or

http://tinyurl.com/5tsb9

>Oxygen is not a combustible gas.

I stated that the hazard was due to the *release* of combustible
gases, which are not ordinarily present in the air-filled tire; this
release is secondary to overheating of the tire. The gases are
generated by the tire compound when the tire gets too hot. The
process is called pyrolysis. The presence of oxygen in the same
cavity sets the stage for the explosions, and several were documented
before the FAA issued the AD requiring nitrogen fill on braked wheels.

> If an air-filled
>tire overheated for any reason, and exploded, it would release a cloud of
>the same gas that was already present on the outside of the tire--AIR.

The explosion was not due to thermal expansion, it was due to
explosive combustion, and what was "released" by the explosion was the
superheated combustion byproduct gas.

>Thought experiment: bury an air-inflated tire in lighted charcoal. The
>tire will heat up, catch fire, and explode.

If ou're expecting this behavior from a car or bike tire, it won't
happen. Talk to a fireman about this. They have to deal with car
fires all the time. An inflated automobile tire exposed to sufficient
heat from an external source will catch fire, rupture (usually in a
localized jet) at the place where the tire compound first melts enough
to allow the casing to split, and then it will continue to burn. I've
watched this a number of times. Car tires don't explode in a fire,
they just pop or hiss (usually the latter), sometimes flare, and then
sag and keep burning. The flare may produce a flame jet several feet
long for a second or two, but that's about it. In theory, it might be
possible to induce a pyrolysis-driven explosion in a car tire, but the
amount of heat needed and the design of the tire (with its thin
sidewalls) will generally produce a nonexplosive failure before the
gas buildup is sufficient to produce an ignition hazard.

Big truck tires are a different matter since they operate at a higher
initial pressure and have a thicker and stronger casing...but they
still usually just pop or hiss and then sag in an *external* fire. If
the heat is transmitted to the tire via the rim, as is often the case
in a brake lockup event, then it's quite possible to get a tire
explosion. (The old two-piece rims produced a different kind of truck
tire explosion hazard in a fire, but that's an unrelated matter.)

Heavy equipment tires are also subject to the same hazard if
overheated sufficiently:

http://www.ohscanada.com/virtual-issue/artucle/tires.html

Note that aviation tires are inflated to well over 200 psi. They are
rated for a burst pressure much higher. Thermal expansion will not
blow them off the rim before the temperature point is reached at which
gassing from the tire compound begins to produce an ignitable charge
inside the tire, assuming that air is present. If the tire is charged
with nitrogen, then the mixture is not ignitable and the hazard is
avoided. If 20% O2 is present initially, the ignition temp is
demonstrably lower than the failure temp of the tire.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

[Werehatrack]

On Sat, 16 Oct 2004 02:05:39 GMT, "Leo Lichtman"
> wrote:

>
>"Werehatrack"(clip)This requirement was imposed due to tire explosions
>resulting from release of combustible gases inside the tire secondary to
>overheating during landings. (clip)
>^^^^^^^^^^^^
>Are you sure about this?

Yes.

Here's the Boeing statement:

http://www.boeing.com/commercial/aeromagazine/aero_05/textonly/m03txt.html

or

http://tinyurl.com/5tsb9

>Oxygen is not a combustible gas.

I stated that the hazard was due to the *release* of combustible
gases, which are not ordinarily present in the air-filled tire; this
release is secondary to overheating of the tire. The gases are
generated by the tire compound when the tire gets too hot. The
process is called pyrolysis. The presence of oxygen in the same
cavity sets the stage for the explosions, and several were documented
before the FAA issued the AD requiring nitrogen fill on braked wheels.

> If an air-filled
>tire overheated for any reason, and exploded, it would release a cloud of
>the same gas that was already present on the outside of the tire--AIR.

The explosion was not due to thermal expansion, it was due to
explosive combustion, and what was "released" by the explosion was the
superheated combustion byproduct gas.

>Thought experiment: bury an air-inflated tire in lighted charcoal. The
>tire will heat up, catch fire, and explode.

If ou're expecting this behavior from a car or bike tire, it won't
happen. Talk to a fireman about this. They have to deal with car
fires all the time. An inflated automobile tire exposed to sufficient
heat from an external source will catch fire, rupture (usually in a
localized jet) at the place where the tire compound first melts enough
to allow the casing to split, and then it will continue to burn. I've
watched this a number of times. Car tires don't explode in a fire,
they just pop or hiss (usually the latter), sometimes flare, and then
sag and keep burning. The flare may produce a flame jet several feet
long for a second or two, but that's about it. In theory, it might be
possible to induce a pyrolysis-driven explosion in a car tire, but the
amount of heat needed and the design of the tire (with its thin
sidewalls) will generally produce a nonexplosive failure before the
gas buildup is sufficient to produce an ignition hazard.

Big truck tires are a different matter since they operate at a higher
initial pressure and have a thicker and stronger casing...but they
still usually just pop or hiss and then sag in an *external* fire. If
the heat is transmitted to the tire via the rim, as is often the case
in a brake lockup event, then it's quite possible to get a tire
explosion. (The old two-piece rims produced a different kind of truck
tire explosion hazard in a fire, but that's an unrelated matter.)

Heavy equipment tires are also subject to the same hazard if
overheated sufficiently:

http://www.ohscanada.com/virtual-issue/artucle/tires.html

Note that aviation tires are inflated to well over 200 psi. They are
rated for a burst pressure much higher. Thermal expansion will not
blow them off the rim before the temperature point is reached at which
gassing from the tire compound begins to produce an ignitable charge
inside the tire, assuming that air is present. If the tire is charged
with nitrogen, then the mixture is not ignitable and the hazard is
avoided. If 20% O2 is present initially, the ignition temp is
demonstrably lower than the failure temp of the tire.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

[Werehatrack]

On Sat, 16 Oct 2004 00:34:30 -0400, Threeducks
> wrote:

>Leo Lichtman wrote:
>> I am convinced it is a gimmick. I picked up the brochure at the Costco tire
>> shop, and studied it. The main "advantage" of nitrogen is that the molecule
>> is slightly heavier than oxygen, so it seeps out of the tire more slowly.
>
>No, the molecular weight of N2 is 28 g/mol while the MW of O2 is 32 g/mol.

I think the intended assertion is that N2 is a larger molecule, and
that it presumably does not escape through the permeable tire material
as fast as a result. This is probably still a spurious claim, since
the difference in diameter is small, on the order of 5% (2.98 vs
3.15x10e-8 cm).

I suspect there's some other factor at work, probably something to do
with somebody having done something damfoolish somewhere that they
don't want to discuss.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

[Werehatrack]

On Sat, 16 Oct 2004 00:34:30 -0400, Threeducks
> wrote:

>Leo Lichtman wrote:
>> I am convinced it is a gimmick. I picked up the brochure at the Costco tire
>> shop, and studied it. The main "advantage" of nitrogen is that the molecule
>> is slightly heavier than oxygen, so it seeps out of the tire more slowly.
>
>No, the molecular weight of N2 is 28 g/mol while the MW of O2 is 32 g/mol.

I think the intended assertion is that N2 is a larger molecule, and
that it presumably does not escape through the permeable tire material
as fast as a result. This is probably still a spurious claim, since
the difference in diameter is small, on the order of 5% (2.98 vs
3.15x10e-8 cm).

I suspect there's some other factor at work, probably something to do
with somebody having done something damfoolish somewhere that they
don't want to discuss.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

[Terry Morse]

Werehatrack wrote:

> If the heat is transmitted to the tire via the rim, as is often
> the case in a brake lockup event, then it's quite possible to get
> a tire explosion.

I don't quite follow that statement. If a brake has locked up,
there is no relative motion between brake and rim, so no energy is
being transmitted through the braking surface and into the rim. All
the energy transfer in a locked-up wheel is between the rubber and
the road.

Or did I misunderstand the meaning of a locked-up brake?
--
terry morse Palo Alto, CA http://bike.terrymorse.com/

[Terry Morse]

Werehatrack wrote:

> If the heat is transmitted to the tire via the rim, as is often
> the case in a brake lockup event, then it's quite possible to get
> a tire explosion.

I don't quite follow that statement. If a brake has locked up,
there is no relative motion between brake and rim, so no energy is
being transmitted through the braking surface and into the rim. All
the energy transfer in a locked-up wheel is between the rubber and
the road.

Or did I misunderstand the meaning of a locked-up brake?
--
terry morse Palo Alto, CA http://bike.terrymorse.com/

[Werehatrack]

On Fri, 15 Oct 2004 22:12:38 -0700, Terry Morse >
wrote:

>Werehatrack wrote:
>
>> If the heat is transmitted to the tire via the rim, as is often
>> the case in a brake lockup event, then it's quite possible to get
>> a tire explosion.
>
>I don't quite follow that statement. If a brake has locked up,
>there is no relative motion between brake and rim, so no energy is
>being transmitted through the braking surface and into the rim. All
>the energy transfer in a locked-up wheel is between the rubber and
>the road.
>
>Or did I misunderstand the meaning of a locked-up brake?

I probably should have used a different term, but it's technically
applicable.

When an air brake on a large truck loses the pressure which holds it
disengaged, the spring in the servo moves the cam to the "lock"
position, but this does not necessarily stop wheel rotation in a
loaded trailer at speed. Instead, the brake fully engages, generating
large amounts of localized heat which can be transmitted through the
hub and rim to the tire. When the truck stops, if there is enough
heat, the tire may ignite...which usually sets the trailer's floor on
fire, since most of those are just wood plank decks. Aluminum trailer
shells can also be ignited in such a fire, resulting in total
destruction of the load and trailer...and the tractor if the driver
doesn't get it unhitched fast enough. If sufficient heat is
transmitted via the rim to the tire before the truck stops, pyrolysis
may produce an explosion hazard, but such bangs are rare in truck
tires. Violent casing failures due to melting of the material from
flexure stress are more common, and they're bad enough even without
the combustion-based explosion hazard found in avaiation and heavy
equipment tires. Once the truck is stopped, the usual course of the
event is for the tire to ignite, burn and then nonexplosively deflate,
assuming it's a modern wheel with a one-piece rim instead of the old
two-piece type.

--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

[Werehatrack]

On Fri, 15 Oct 2004 22:12:38 -0700, Terry Morse >
wrote:

>Werehatrack wrote:
>
>> If the heat is transmitted to the tire via the rim, as is often
>> the case in a brake lockup event, then it's quite possible to get
>> a tire explosion.
>
>I don't quite follow that statement. If a brake has locked up,
>there is no relative motion between brake and rim, so no energy is
>being transmitted through the braking surface and into the rim. All
>the energy transfer in a locked-up wheel is between the rubber and
>the road.
>
>Or did I misunderstand the meaning of a locked-up brake?

I probably should have used a different term, but it's technically
applicable.

When an air brake on a large truck loses the pressure which holds it
disengaged, the spring in the servo moves the cam to the "lock"
position, but this does not necessarily stop wheel rotation in a
loaded trailer at speed. Instead, the brake fully engages, generating
large amounts of localized heat which can be transmitted through the
hub and rim to the tire. When the truck stops, if there is enough
heat, the tire may ignite...which usually sets the trailer's floor on
fire, since most of those are just wood plank decks. Aluminum trailer
shells can also be ignited in such a fire, resulting in total
destruction of the load and trailer...and the tractor if the driver
doesn't get it unhitched fast enough. If sufficient heat is
transmitted via the rim to the tire before the truck stops, pyrolysis
may produce an explosion hazard, but such bangs are rare in truck
tires. Violent casing failures due to melting of the material from
flexure stress are more common, and they're bad enough even without
the combustion-based explosion hazard found in avaiation and heavy
equipment tires. Once the truck is stopped, the usual course of the
event is for the tire to ignite, burn and then nonexplosively deflate,
assuming it's a modern wheel with a one-piece rim instead of the old
two-piece type.

--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

[[email protected]]

On Sat, 16 Oct 2004 04:48:58 GMT, Werehatrack
> wrote:

>On Sat, 16 Oct 2004 00:34:30 -0400, Threeducks
> wrote:
>
>>Leo Lichtman wrote:
>>> I am convinced it is a gimmick. I picked up the brochure at the Costco tire
>>> shop, and studied it. The main "advantage" of nitrogen is that the molecule
>>> is slightly heavier than oxygen, so it seeps out of the tire more slowly.
>>
>>No, the molecular weight of N2 is 28 g/mol while the MW of O2 is 32 g/mol.
>
>I think the intended assertion is that N2 is a larger molecule, and
>that it presumably does not escape through the permeable tire material
>as fast as a result. This is probably still a spurious claim, since
>the difference in diameter is small, on the order of 5% (2.98 vs
>3.15x10e-8 cm).
>
>I suspect there's some other factor at work, probably something to do
>with somebody having done something damfoolish somewhere that they
>don't want to discuss.

Dear Lion, DuckTrio, and Wereratpack,

In the thread that I mentioned, Peter explained:

"The greater permeation rate of carbon dioxide is due to its
high solubility in rubber as a result of the affinity of the
carbon dioxide molecules for the long carbon chains in the
rubber. Nitrogen and oxygen molecules tend to bounce off the
rubber but carbon dioxide molecules stick to it and become
absorbed by the rubber. They are then able to slowly
migrate through the rubber and eventually escape from the
tube. See
http://www.madsci.org/posts/archives/may98/895552329.Ch.r.html
for additional description."

http://groups.google.com/groups?hl=en&lr=&selm=Js-dnXZs8pWPXa_cRVn-sg%40comcast.com

or

http://tinyurl.com/56x9u

So the seepage rates may be a matter of chemical affinity,
not the size of the molecules.

The link cited shows nitrogen's permeability rate for rubber
at only 9.43 something-or-others, while oxygen is much more
eager to pass through at 23.3, and carbon dioxide goes
through rubber like cr--er, bacon through a goose at 153.

Carl Fogel

[[email protected]]

On Sat, 16 Oct 2004 04:48:58 GMT, Werehatrack
> wrote:

>On Sat, 16 Oct 2004 00:34:30 -0400, Threeducks
> wrote:
>
>>Leo Lichtman wrote:
>>> I am convinced it is a gimmick. I picked up the brochure at the Costco tire
>>> shop, and studied it. The main "advantage" of nitrogen is that the molecule
>>> is slightly heavier than oxygen, so it seeps out of the tire more slowly.
>>
>>No, the molecular weight of N2 is 28 g/mol while the MW of O2 is 32 g/mol.
>
>I think the intended assertion is that N2 is a larger molecule, and
>that it presumably does not escape through the permeable tire material
>as fast as a result. This is probably still a spurious claim, since
>the difference in diameter is small, on the order of 5% (2.98 vs
>3.15x10e-8 cm).
>
>I suspect there's some other factor at work, probably something to do
>with somebody having done something damfoolish somewhere that they
>don't want to discuss.

Dear Lion, DuckTrio, and Wereratpack,

In the thread that I mentioned, Peter explained:

"The greater permeation rate of carbon dioxide is due to its
high solubility in rubber as a result of the affinity of the
carbon dioxide molecules for the long carbon chains in the
rubber. Nitrogen and oxygen molecules tend to bounce off the
rubber but carbon dioxide molecules stick to it and become
absorbed by the rubber. They are then able to slowly
migrate through the rubber and eventually escape from the
tube. See
http://www.madsci.org/posts/archives/may98/895552329.Ch.r.html
for additional description."

http://groups.google.com/groups?hl=en&lr=&selm=Js-dnXZs8pWPXa_cRVn-sg%40comcast.com

or

http://tinyurl.com/56x9u

So the seepage rates may be a matter of chemical affinity,
not the size of the molecules.

The link cited shows nitrogen's permeability rate for rubber
at only 9.43 something-or-others, while oxygen is much more
eager to pass through at 23.3, and carbon dioxide goes
through rubber like cr--er, bacon through a goose at 153.

Carl Fogel

[Leo Lichtman]

"Werehatrack" wrote : "Yes," in response to Leo's question, "Are you sure
about this?"
^^^^^^^^^^^^^^^^^
From what you have written, it is clear that you are knowlegeable on this
topic--I believe you now. From the fact that you have seen a number of
tires rupture in car fires, and the authority with which you speak on this
subject, I assume that this is professional expertese. Are you a
firefighter? Would you mind filling us in?

[Leo Lichtman]

"Werehatrack" wrote : "Yes," in response to Leo's question, "Are you sure
about this?"
^^^^^^^^^^^^^^^^^
From what you have written, it is clear that you are knowlegeable on this
topic--I believe you now. From the fact that you have seen a number of
tires rupture in car fires, and the authority with which you speak on this
subject, I assume that this is professional expertese. Are you a
firefighter? Would you mind filling us in?

[Jim Smith]

Werehatrack > writes:

> On Sat, 16 Oct 2004 00:34:30 -0400, Threeducks
> > wrote:
>
> >Leo Lichtman wrote:
> >> I am convinced it is a gimmick. I picked up the brochure at the Costco tire
> >> shop, and studied it. The main "advantage" of nitrogen is that the molecule
> >> is slightly heavier than oxygen, so it seeps out of the tire more slowly.
> >
> >No, the molecular weight of N2 is 28 g/mol while the MW of O2 is 32 g/mol.
>
> I think the intended assertion is that N2 is a larger molecule, and
> that it presumably does not escape through the permeable tire material
> as fast as a result. This is probably still a spurious claim, since
> the difference in diameter is small, on the order of 5% (2.98 vs
> 3.15x10e-8 cm).

If you go by the Van der Waals "b" constant, N2 is about 22% greater
volume than O2 (32 vs 39) which is about a 5% difference in diameter,
but it sounds bigger. The permeability of N2 is less than that of O2
in all organic polymers I have ever seen figures for, by a factor on
the order of 10 which varies depending on the polymer.

Permeability is the product of the solubility and the diffusion
coefficient, both of which both seem to be smaller for N2 in a wide
range of organic polymers, but the ratios to O2 seem to vary quite a
bit so there must be more going on than just the size difference.

[Jim Smith]

Werehatrack > writes:

> On Sat, 16 Oct 2004 00:34:30 -0400, Threeducks
> > wrote:
>
> >Leo Lichtman wrote:
> >> I am convinced it is a gimmick. I picked up the brochure at the Costco tire
> >> shop, and studied it. The main "advantage" of nitrogen is that the molecule
> >> is slightly heavier than oxygen, so it seeps out of the tire more slowly.
> >
> >No, the molecular weight of N2 is 28 g/mol while the MW of O2 is 32 g/mol.
>
> I think the intended assertion is that N2 is a larger molecule, and
> that it presumably does not escape through the permeable tire material
> as fast as a result. This is probably still a spurious claim, since
> the difference in diameter is small, on the order of 5% (2.98 vs
> 3.15x10e-8 cm).

If you go by the Van der Waals "b" constant, N2 is about 22% greater
volume than O2 (32 vs 39) which is about a 5% difference in diameter,
but it sounds bigger. The permeability of N2 is less than that of O2
in all organic polymers I have ever seen figures for, by a factor on
the order of 10 which varies depending on the polymer.

Permeability is the product of the solubility and the diffusion
coefficient, both of which both seem to be smaller for N2 in a wide
range of organic polymers, but the ratios to O2 seem to vary quite a
bit so there must be more going on than just the size difference.

[Jim Smith]

writes:

> On Sat, 16 Oct 2004 04:48:58 GMT, Werehatrack
> > wrote:
>
> >On Sat, 16 Oct 2004 00:34:30 -0400, Threeducks
> > wrote:
> >
> >>Leo Lichtman wrote:
> >>> I am convinced it is a gimmick. I picked up the brochure at the Costco tire
> >>> shop, and studied it. The main "advantage" of nitrogen is that the molecule
> >>> is slightly heavier than oxygen, so it seeps out of the tire more slowly.
> >>
> >>No, the molecular weight of N2 is 28 g/mol while the MW of O2 is 32 g/mol.
> >
> >I think the intended assertion is that N2 is a larger molecule, and
> >that it presumably does not escape through the permeable tire material
> >as fast as a result. This is probably still a spurious claim, since
> >the difference in diameter is small, on the order of 5% (2.98 vs
> >3.15x10e-8 cm).
> >
> >I suspect there's some other factor at work, probably something to do
> >with somebody having done something damfoolish somewhere that they
> >don't want to discuss.
>
> Dear Lion, DuckTrio, and Wereratpack,
>
> In the thread that I mentioned, Peter explained:
>
> "The greater permeation rate of carbon dioxide is due to its
> high solubility in rubber as a result of the affinity of the
> carbon dioxide molecules for the long carbon chains in the
> rubber. Nitrogen and oxygen molecules tend to bounce off the
> rubber but carbon dioxide molecules stick to it and become
> absorbed by the rubber. They are then able to slowly
> migrate through the rubber and eventually escape from the
> tube. See
> http://www.madsci.org/posts/archives/may98/895552329.Ch.r.html
> for additional description."
>
> http://groups.google.com/groups?hl=en&lr=&selm=Js-dnXZs8pWPXa_cRVn-sg%40comcast.com
>
> or
>
> http://tinyurl.com/56x9u
>
> So the seepage rates may be a matter of chemical affinity,
> not the size of the molecules.
>
> The link cited shows nitrogen's permeability rate for rubber
> at only 9.43 something-or-others, while oxygen is much more
> eager to pass through at 23.3, and carbon dioxide goes
> through rubber like cr--er, bacon through a goose at 153.

CO2 is a polar molecule while both O2 and N2 are not, so one would
expect to see a big differance with CO2. In other words, O2 and N2
are much more like each other than either is like CO2.

[Jim Smith]

writes:

> On Sat, 16 Oct 2004 04:48:58 GMT, Werehatrack
> > wrote:
>
> >On Sat, 16 Oct 2004 00:34:30 -0400, Threeducks
> > wrote:
> >
> >>Leo Lichtman wrote:
> >>> I am convinced it is a gimmick. I picked up the brochure at the Costco tire
> >>> shop, and studied it. The main "advantage" of nitrogen is that the molecule
> >>> is slightly heavier than oxygen, so it seeps out of the tire more slowly.
> >>
> >>No, the molecular weight of N2 is 28 g/mol while the MW of O2 is 32 g/mol.
> >
> >I think the intended assertion is that N2 is a larger molecule, and
> >that it presumably does not escape through the permeable tire material
> >as fast as a result. This is probably still a spurious claim, since
> >the difference in diameter is small, on the order of 5% (2.98 vs
> >3.15x10e-8 cm).
> >
> >I suspect there's some other factor at work, probably something to do
> >with somebody having done something damfoolish somewhere that they
> >don't want to discuss.
>
> Dear Lion, DuckTrio, and Wereratpack,
>
> In the thread that I mentioned, Peter explained:
>
> "The greater permeation rate of carbon dioxide is due to its
> high solubility in rubber as a result of the affinity of the
> carbon dioxide molecules for the long carbon chains in the
> rubber. Nitrogen and oxygen molecules tend to bounce off the
> rubber but carbon dioxide molecules stick to it and become
> absorbed by the rubber. They are then able to slowly
> migrate through the rubber and eventually escape from the
> tube. See
> http://www.madsci.org/posts/archives/may98/895552329.Ch.r.html
> for additional description."
>
> http://groups.google.com/groups?hl=en&lr=&selm=Js-dnXZs8pWPXa_cRVn-sg%40comcast.com
>
> or
>
> http://tinyurl.com/56x9u
>
> So the seepage rates may be a matter of chemical affinity,
> not the size of the molecules.
>
> The link cited shows nitrogen's permeability rate for rubber
> at only 9.43 something-or-others, while oxygen is much more
> eager to pass through at 23.3, and carbon dioxide goes
> through rubber like cr--er, bacon through a goose at 153.

CO2 is a polar molecule while both O2 and N2 are not, so one would
expect to see a big differance with CO2. In other words, O2 and N2
are much more like each other than either is like CO2.

[papercut]

"Leo Lichtman" > wrote in message
> Thought experiment: bury an air-inflated tire in lighted charcoal. The
> tire will heat up, catch fire, and explode. The charcoal will scatter, and
> glow slightly brighter for a fraction of a second, due to the blowing of air
> from within the pile. No further explosion would occur.


This reminded me of some knuckleheads I knew in college. Somehow,
they'd gotten the idea that those floating party balloons were filled
with hydrogen, which being lighter than air, made them float. To prove
this, they proceeded to hold a lit match to the balloon, which
promptly popped and thus declared a hydrogen "explosion". All attempts
to explain that the balloons simply popped as the *helium* inside was
unlikely to ignite under any such casual circumstance, fell on deaf
ears. This incident makes my eyes roll to this day.

Regarding the nitrogen in auto tires, Does one have to evacuate all
the air in the tire before filling it with nitrogen in order to get
the claimed benefits? How does one do this with a modern tubeless
tire? How much does one have to pay for the privledge of being taken
in by this?

[papercut]

"Leo Lichtman" > wrote in message
> Thought experiment: bury an air-inflated tire in lighted charcoal. The
> tire will heat up, catch fire, and explode. The charcoal will scatter, and
> glow slightly brighter for a fraction of a second, due to the blowing of air
> from within the pile. No further explosion would occur.


This reminded me of some knuckleheads I knew in college. Somehow,
they'd gotten the idea that those floating party balloons were filled
with hydrogen, which being lighter than air, made them float. To prove
this, they proceeded to hold a lit match to the balloon, which
promptly popped and thus declared a hydrogen "explosion". All attempts
to explain that the balloons simply popped as the *helium* inside was
unlikely to ignite under any such casual circumstance, fell on deaf
ears. This incident makes my eyes roll to this day.

Regarding the nitrogen in auto tires, Does one have to evacuate all
the air in the tire before filling it with nitrogen in order to get
the claimed benefits? How does one do this with a modern tubeless
tire? How much does one have to pay for the privledge of being taken
in by this?

[[email protected]]

Rault who? writes:

>>> If the heat is transmitted to the tire via the rim, as is often
>>> the case in a brake lockup event, then it's quite possible to get
>>> a tire explosion.

>> I don't quite follow that statement. If a brake has locked up,
>> there is no relative motion between brake and rim, so no energy is
>> being transmitted through the braking surface and into the rim. All
>> the energy transfer in a locked-up wheel is between the rubber and
>> the road.

>> Or did I misunderstand the meaning of a locked-up brake?

> I probably should have used a different term, but it's technically
> applicable.

> When an air brake on a large truck loses the pressure which holds it
> disengaged, the spring in the servo moves the cam to the "lock"
> position, but this does not necessarily stop wheel rotation in a
> loaded trailer at speed. Instead, the brake fully engages, generating
> large amounts of localized heat which can be transmitted through the
> hub and rim to the tire.

Two points here.

First, truck tires skid easily under full brake application as we see
by the long dual skid marks on highways, so lock-up would not generate
brake heat.

Second, brake drums are substantially far away from rim beds, where
tire inflation air could be heated, to have any effect.

Besides, what is "localized heat" from braking? The heat path from
brake drum to tire is via the rim dish that has a long\ thermal path to
pressurized air.

> When the truck stops, if there is enough heat, the tire may
> ignite... which usually sets the trailer's floor on fire, since most
> of those are just wood plank decks. Aluminum trailer shells can
> also be ignited in such a fire, resulting in total destruction of
> the load and trailer... and the tractor if the driver doesn't get it
> unhitched fast enough.

When does aluminum burn in air? Fires on trailers are caused by
something else catching fire and it is not tires but rather grease in
wheels that can make flames that ignite tires.

> If sufficient heat is transmitted via the rim to the tire before the
> truck stops, pyrolysis may produce an explosion hazard, but such
> bangs are rare in truck tires. Violent casing failures due to
> melting of the material from flexure stress are more common, and
> they're bad enough even without the combustion-based explosion
> hazard found in avaiation and heavy equipment tires.

Please explain flexture stress and how it generates enough heat to
ignite a tire. You should be aware that aviation brakes are not in
the least like truck brakes.

> Once the truck is stopped, the usual course of the event is for the
> tire to ignite, burn and then nonexplosively deflate, assuming it's
> a modern wheel with a one-piece rim instead of the old two-piece
> type.

You mean boutique aluminum wheels instead of durable utilitarian steel
wheels which are made of a hoop and rim dish. Just the same, it is
not the brake heat that ignites the tire itself.

Jobst Brandt

[[email protected]]

Rault who? writes:

>>> If the heat is transmitted to the tire via the rim, as is often
>>> the case in a brake lockup event, then it's quite possible to get
>>> a tire explosion.

>> I don't quite follow that statement. If a brake has locked up,
>> there is no relative motion between brake and rim, so no energy is
>> being transmitted through the braking surface and into the rim. All
>> the energy transfer in a locked-up wheel is between the rubber and
>> the road.

>> Or did I misunderstand the meaning of a locked-up brake?

> I probably should have used a different term, but it's technically
> applicable.

> When an air brake on a large truck loses the pressure which holds it
> disengaged, the spring in the servo moves the cam to the "lock"
> position, but this does not necessarily stop wheel rotation in a
> loaded trailer at speed. Instead, the brake fully engages, generating
> large amounts of localized heat which can be transmitted through the
> hub and rim to the tire.

Two points here.

First, truck tires skid easily under full brake application as we see
by the long dual skid marks on highways, so lock-up would not generate
brake heat.

Second, brake drums are substantially far away from rim beds, where
tire inflation air could be heated, to have any effect.

Besides, what is "localized heat" from braking? The heat path from
brake drum to tire is via the rim dish that has a long\ thermal path to
pressurized air.

> When the truck stops, if there is enough heat, the tire may
> ignite... which usually sets the trailer's floor on fire, since most
> of those are just wood plank decks. Aluminum trailer shells can
> also be ignited in such a fire, resulting in total destruction of
> the load and trailer... and the tractor if the driver doesn't get it
> unhitched fast enough.

When does aluminum burn in air? Fires on trailers are caused by
something else catching fire and it is not tires but rather grease in
wheels that can make flames that ignite tires.

> If sufficient heat is transmitted via the rim to the tire before the
> truck stops, pyrolysis may produce an explosion hazard, but such
> bangs are rare in truck tires. Violent casing failures due to
> melting of the material from flexure stress are more common, and
> they're bad enough even without the combustion-based explosion
> hazard found in avaiation and heavy equipment tires.

Please explain flexture stress and how it generates enough heat to
ignite a tire. You should be aware that aviation brakes are not in
the least like truck brakes.

> Once the truck is stopped, the usual course of the event is for the
> tire to ignite, burn and then nonexplosively deflate, assuming it's
> a modern wheel with a one-piece rim instead of the old two-piece
> type.

You mean boutique aluminum wheels instead of durable utilitarian steel
wheels which are made of a hoop and rim dish. Just the same, it is
not the brake heat that ignites the tire itself.

Jobst Brandt

[Ray Heindl]

"Leo Lichtman" > wrote:

> IMO, Costco is spending money on nitrogen in order to improve tire
> sales.

Maybe they didn't spend any money on nitrogen. Signs and brochures are
a lot cheaper than nitrogen tanks.

--
Ray Heindl
(remove the Xs to reply to: )

[Ray Heindl]

"Leo Lichtman" > wrote:

> IMO, Costco is spending money on nitrogen in order to improve tire
> sales.

Maybe they didn't spend any money on nitrogen. Signs and brochures are
a lot cheaper than nitrogen tanks.

--
Ray Heindl
(remove the Xs to reply to: )

[B.B.]

In article >,
Erik Freitag > wrote:

>My local Costco is advertising their use of nitrogen for automobile tire
>inflation. They say nitrogen is a dry, inert gas used to inflate airplane
>tires, off-road truck tires, military vehicle tires and race car tires for
>improved performance.
>
>Apparently, the oxygen in compressed air is bad for tires, and I assume,
>tubes.
>
>So, does topeak or zefal make a reasonably priced, frame-mounted nitrogen
>generator?

The just hashed this out in news:rec.autos.tech a little while back.
http://groups.google.com/groups?hl=en&lr=&c2coff=1&safe=off&threadm=4ot7k
0tlm8s4dehuhss7epji6nfl470a45%404ax.com&rnum=1&prev=/groups%3Fsafe%3Doff%
26as_ugroup%3Drec.autos.tech%26as_usubject%3Dnitro gen%26as_drrb%3Dq%26as_
qdr%3Dm3%26lr%3D%26hl%3Den
Or http://tinyurl.com/692gh as the URL's friends know him.
Anyway, the gist is that you have more pressure stability as your
tire heats up because the compressed nitrogen is dry. That's it. No
molecular diffusion BS (though CO2 does diffuse through rubber rather
quickly), no oxygen dissolving things, no weight changes, no nothing.
So, it's a gimmick.

--
B.B. --I am not a goat! thegoat4 at airmail.net

[B.B.]

In article >,
Erik Freitag > wrote:

>My local Costco is advertising their use of nitrogen for automobile tire
>inflation. They say nitrogen is a dry, inert gas used to inflate airplane
>tires, off-road truck tires, military vehicle tires and race car tires for
>improved performance.
>
>Apparently, the oxygen in compressed air is bad for tires, and I assume,
>tubes.
>
>So, does topeak or zefal make a reasonably priced, frame-mounted nitrogen
>generator?

The just hashed this out in news:rec.autos.tech a little while back.
http://groups.google.com/groups?hl=en&lr=&c2coff=1&safe=off&threadm=4ot7k
0tlm8s4dehuhss7epji6nfl470a45%404ax.com&rnum=1&prev=/groups%3Fsafe%3Doff%
26as_ugroup%3Drec.autos.tech%26as_usubject%3Dnitro gen%26as_drrb%3Dq%26as_
qdr%3Dm3%26lr%3D%26hl%3Den
Or http://tinyurl.com/692gh as the URL's friends know him.
Anyway, the gist is that you have more pressure stability as your
tire heats up because the compressed nitrogen is dry. That's it. No
molecular diffusion BS (though CO2 does diffuse through rubber rather
quickly), no oxygen dissolving things, no weight changes, no nothing.
So, it's a gimmick.

--
B.B. --I am not a goat! thegoat4 at airmail.net

[Threeducks]

Jim Smith wrote:
> writes:
>
>
>>On Sat, 16 Oct 2004 04:48:58 GMT, Werehatrack
> wrote:
>>
>>
>>>On Sat, 16 Oct 2004 00:34:30 -0400, Threeducks
> wrote:
>>>
>>>
>>>>Leo Lichtman wrote:
>>>>
>>>>>I am convinced it is a gimmick. I picked up the brochure at the Costco tire
>>>>>shop, and studied it. The main "advantage" of nitrogen is that the molecule
>>>>>is slightly heavier than oxygen, so it seeps out of the tire more slowly.
>>>>
>>>>No, the molecular weight of N2 is 28 g/mol while the MW of O2 is 32 g/mol.
>>>
>>>I think the intended assertion is that N2 is a larger molecule, and
>>>that it presumably does not escape through the permeable tire material
>>>as fast as a result. This is probably still a spurious claim, since
>>>the difference in diameter is small, on the order of 5% (2.98 vs
>>>3.15x10e-8 cm).
>>>
>>>I suspect there's some other factor at work, probably something to do
>>>with somebody having done something damfoolish somewhere that they
>>>don't want to discuss.
>>
>>Dear Lion, DuckTrio, and Wereratpack,
>>
>>In the thread that I mentioned, Peter explained:
>>
>>"The greater permeation rate of carbon dioxide is due to its
>>high solubility in rubber as a result of the affinity of the
>>carbon dioxide molecules for the long carbon chains in the
>>rubber. Nitrogen and oxygen molecules tend to bounce off the
>>rubber but carbon dioxide molecules stick to it and become
>>absorbed by the rubber. They are then able to slowly
>>migrate through the rubber and eventually escape from the
>>tube. See
>>http://www.madsci.org/posts/archives/may98/895552329.Ch.r.html
>>for additional description."
>>
>>http://groups.google.com/groups?hl=en&lr=&selm=Js-dnXZs8pWPXa_cRVn-sg%40comcast.com
>>
>>or
>>
>>http://tinyurl.com/56x9u
>>
>>So the seepage rates may be a matter of chemical affinity,
>>not the size of the molecules.
>>
>>The link cited shows nitrogen's permeability rate for rubber
>>at only 9.43 something-or-others, while oxygen is much more
>>eager to pass through at 23.3, and carbon dioxide goes
>>through rubber like cr--er, bacon through a goose at 153.
>
>
> CO2 is a polar molecule while both O2 and N2 are not, so one would
> expect to see a big differance with CO2. In other words, O2 and N2
> are much more like each other than either is like CO2.
>

Wrong. All of those molecules have significant quadrupole moments, but
no dipole moment. The major difference between these molecules is in
the strength of the intermolecular interactions. CO2 has a critical
temperature near room temperature (305 K), while the critical
temperature for N2 is around 130 K and O2 is 155 K.

[Threeducks]

Jim Smith wrote:
> writes:
>
>
>>On Sat, 16 Oct 2004 04:48:58 GMT, Werehatrack
> wrote:
>>
>>
>>>On Sat, 16 Oct 2004 00:34:30 -0400, Threeducks
> wrote:
>>>
>>>
>>>>Leo Lichtman wrote:
>>>>
>>>>>I am convinced it is a gimmick. I picked up the brochure at the Costco tire
>>>>>shop, and studied it. The main "advantage" of nitrogen is that the molecule
>>>>>is slightly heavier than oxygen, so it seeps out of the tire more slowly.
>>>>
>>>>No, the molecular weight of N2 is 28 g/mol while the MW of O2 is 32 g/mol.
>>>
>>>I think the intended assertion is that N2 is a larger molecule, and
>>>that it presumably does not escape through the permeable tire material
>>>as fast as a result. This is probably still a spurious claim, since
>>>the difference in diameter is small, on the order of 5% (2.98 vs
>>>3.15x10e-8 cm).
>>>
>>>I suspect there's some other factor at work, probably something to do
>>>with somebody having done something damfoolish somewhere that they
>>>don't want to discuss.
>>
>>Dear Lion, DuckTrio, and Wereratpack,
>>
>>In the thread that I mentioned, Peter explained:
>>
>>"The greater permeation rate of carbon dioxide is due to its
>>high solubility in rubber as a result of the affinity of the
>>carbon dioxide molecules for the long carbon chains in the
>>rubber. Nitrogen and oxygen molecules tend to bounce off the
>>rubber but carbon dioxide molecules stick to it and become
>>absorbed by the rubber. They are then able to slowly
>>migrate through the rubber and eventually escape from the
>>tube. See
>>http://www.madsci.org/posts/archives/may98/895552329.Ch.r.html
>>for additional description."
>>
>>http://groups.google.com/groups?hl=en&lr=&selm=Js-dnXZs8pWPXa_cRVn-sg%40comcast.com
>>
>>or
>>
>>http://tinyurl.com/56x9u
>>
>>So the seepage rates may be a matter of chemical affinity,
>>not the size of the molecules.
>>
>>The link cited shows nitrogen's permeability rate for rubber
>>at only 9.43 something-or-others, while oxygen is much more
>>eager to pass through at 23.3, and carbon dioxide goes
>>through rubber like cr--er, bacon through a goose at 153.
>
>
> CO2 is a polar molecule while both O2 and N2 are not, so one would
> expect to see a big differance with CO2. In other words, O2 and N2
> are much more like each other than either is like CO2.
>

Wrong. All of those molecules have significant quadrupole moments, but
no dipole moment. The major difference between these molecules is in
the strength of the intermolecular interactions. CO2 has a critical
temperature near room temperature (305 K), while the critical
temperature for N2 is around 130 K and O2 is 155 K.

[B.B.]

In article >,
wrote:

[...]

>> When an air brake on a large truck loses the pressure which holds it
>> disengaged, the spring in the servo moves the cam to the "lock"
>> position, but this does not necessarily stop wheel rotation in a
>> loaded trailer at speed. Instead, the brake fully engages, generating
>> large amounts of localized heat which can be transmitted through the
>> hub and rim to the tire.
>
>Two points here.
>
>First, truck tires skid easily under full brake application as we see
>by the long dual skid marks on highways, so lock-up would not generate
>brake heat.

Depends on the load and the application pressure. Spring brakes have
significantly less ultimate braking power than the service brake
chambers. Most of the time it's about half. And there are always more
axles with service brakes than parking brakes.
With a heavy enough load even the service brakes won't keep the
wheels from turning. And even though it's illegal and stupid, many
drivers turn up their fuel systems to boost horsepower. Some of them go
far enough that the truck fully loaded in a low gear can pull right
through its brakes.
So, yeah, lock-up can generate lots of heat from the brakes.
Those skid marks usually come from a lost supply line to the trailer
air brakes, causing the trailing axles to "park." Most of the time that
back axle will be lightly loaded compared to the axles under the front
of the trailer. Drivers are supposed to balance the axles, but few do
since it's a big pain in the ass. Leaving you with one axle that's very
likely to leave skid marks, and a bunch of axles that aren't. If you
ever come to a site where a truck skidded to a stop on purpose by way of
service brakes you'll notice a whole bunch of skid marks and it'll look
like several trucks stopped in the same place. Most trucks have ABS now
anyway, so those solid skid marks can only be generated by the failure
mode and that's almost always from a lost trailer air line.

>Second, brake drums are substantially far away from rim beds, where
>tire inflation air could be heated, to have any effect.
>
>Besides, what is "localized heat" from braking? The heat path from
>brake drum to tire is via the rim dish that has a long\ thermal path to
>pressurized air.

I don't think that gap is substantial enough. I know it's a air gap
and all, but that's a lot of heat being radiated. Truck tires do catch
fire from excessively prolonged braking, so that heat must be getting
across somehow. I figure it's through sheer brute force of enough heat
to overcome any sort of inefficiency in transmission.

[...]

--
B.B. --I am not a goat! thegoat4 at airmail.net

[B.B.]

In article >,
wrote:

[...]

>> When an air brake on a large truck loses the pressure which holds it
>> disengaged, the spring in the servo moves the cam to the "lock"
>> position, but this does not necessarily stop wheel rotation in a
>> loaded trailer at speed. Instead, the brake fully engages, generating
>> large amounts of localized heat which can be transmitted through the
>> hub and rim to the tire.
>
>Two points here.
>
>First, truck tires skid easily under full brake application as we see
>by the long dual skid marks on highways, so lock-up would not generate
>brake heat.

Depends on the load and the application pressure. Spring brakes have
significantly less ultimate braking power than the service brake
chambers. Most of the time it's about half. And there are always more
axles with service brakes than parking brakes.
With a heavy enough load even the service brakes won't keep the
wheels from turning. And even though it's illegal and stupid, many
drivers turn up their fuel systems to boost horsepower. Some of them go
far enough that the truck fully loaded in a low gear can pull right
through its brakes.
So, yeah, lock-up can generate lots of heat from the brakes.
Those skid marks usually come from a lost supply line to the trailer
air brakes, causing the trailing axles to "park." Most of the time that
back axle will be lightly loaded compared to the axles under the front
of the trailer. Drivers are supposed to balance the axles, but few do
since it's a big pain in the ass. Leaving you with one axle that's very
likely to leave skid marks, and a bunch of axles that aren't. If you
ever come to a site where a truck skidded to a stop on purpose by way of
service brakes you'll notice a whole bunch of skid marks and it'll look
like several trucks stopped in the same place. Most trucks have ABS now
anyway, so those solid skid marks can only be generated by the failure
mode and that's almost always from a lost trailer air line.

>Second, brake drums are substantially far away from rim beds, where
>tire inflation air could be heated, to have any effect.
>
>Besides, what is "localized heat" from braking? The heat path from
>brake drum to tire is via the rim dish that has a long\ thermal path to
>pressurized air.

I don't think that gap is substantial enough. I know it's a air gap
and all, but that's a lot of heat being radiated. Truck tires do catch
fire from excessively prolonged braking, so that heat must be getting
across somehow. I figure it's through sheer brute force of enough heat
to overcome any sort of inefficiency in transmission.

[...]

--
B.B. --I am not a goat! thegoat4 at airmail.net

[Werehatrack]

On Sat, 16 Oct 2004 16:16:41 -0500, "B.B."
> wrote:

>In article >,
> wrote:
>
>>Two points here.
>>
>>First, truck tires skid easily under full brake application as we see
>>by the long dual skid marks on highways,

Not true if running at, near, or over max load. Trailer axle brakes
are usually not as effective as those on the tractor, and most of
those skid marks you see are from an unloaded trailer.

>>so lock-up would not generate
>>brake heat.
>
> Depends on the load and the application pressure. Spring brakes have
>significantly less ultimate braking power than the service brake
>chambers. Most of the time it's about half. And there are always more
>axles with service brakes than parking brakes.
> With a heavy enough load even the service brakes won't keep the
>wheels from turning.

And high loads also make the tires run hot to begin with.

>And even though it's illegal and stupid, many
>drivers turn up their fuel systems to boost horsepower. Some of them go
>far enough that the truck fully loaded in a low gear can pull right
>through its brakes.
> So, yeah, lock-up can generate lots of heat from the brakes.

Enough to heat the drums, which are usually at least partway inside
the dish of the inner wheel, to a nice red glow.

> Those skid marks usually come from a lost supply line to the trailer
>air brakes, causing the trailing axles to "park." Most of the time that
>back axle will be lightly loaded compared to the axles under the front
>of the trailer.

Unless, as you noted, the truck is running with a full load, in which
case the rear axles may be loaded heavily unless the driver has
shifted the axles rearward, which he should have for non-city running.

> Drivers are supposed to balance the axles, but few do
>since it's a big pain in the ass.

Worse, with a partial load, it may not be possible to put any
significant weight to the rear. Load stops and straps or not, when
all you have is a handful of damned heavy pallets, they'll be up front
unless it's on a flatbed where there are a lot more tie-down options.

>Leaving you with one axle that's very
>likely to leave skid marks, and a bunch of axles that aren't. If you
>ever come to a site where a truck skidded to a stop on purpose by way of
>service brakes you'll notice a whole bunch of skid marks and it'll look
>like several trucks stopped in the same place. Most trucks have ABS now
>anyway, so those solid skid marks can only be generated by the failure
>mode and that's almost always from a lost trailer air line.

Bingo. It's a common enough failure that many drivers carry spares
for all three lines, and they're typically sold at most truck stops as
well.

>>Second, brake drums are substantially far away from rim beds, where
>>tire inflation air could be heated, to have any effect.

A brake drum at 900F which is in the vertical plane of the inner
wheel's frameward bead is quite capable of heating that tire to the
point where the surface begins to melt, which then drips onto the
brake drum and ignites.

>>Besides, what is "localized heat" from braking? The heat path from
>>brake drum to tire is via the rim dish that has a long\ thermal path to
>>pressurized air.
>
> I don't think that gap is substantial enough. I know it's a air gap
>and all, but that's a lot of heat being radiated. Truck tires do catch
>fire from excessively prolonged braking, so that heat must be getting
>across somehow. I figure it's through sheer brute force of enough heat
>to overcome any sort of inefficiency in transmission.

Yes. I regularly see the results of such fires in my travels. It
does, indeed, happen. The retired truck driver who lives across the
street has said on more than on occasion that a trailer brake overheat
may occur without the driver being aware of what's going on until it's
too late to do anything but stop, unhitch and hope. I've seen what
happens if the driver fails to unhitch a couple of times as well.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

[Werehatrack]

On Sat, 16 Oct 2004 16:16:41 -0500, "B.B."
> wrote:

>In article >,
> wrote:
>
>>Two points here.
>>
>>First, truck tires skid easily under full brake application as we see
>>by the long dual skid marks on highways,

Not true if running at, near, or over max load. Trailer axle brakes
are usually not as effective as those on the tractor, and most of
those skid marks you see are from an unloaded trailer.

>>so lock-up would not generate
>>brake heat.
>
> Depends on the load and the application pressure. Spring brakes have
>significantly less ultimate braking power than the service brake
>chambers. Most of the time it's about half. And there are always more
>axles with service brakes than parking brakes.
> With a heavy enough load even the service brakes won't keep the
>wheels from turning.

And high loads also make the tires run hot to begin with.

>And even though it's illegal and stupid, many
>drivers turn up their fuel systems to boost horsepower. Some of them go
>far enough that the truck fully loaded in a low gear can pull right
>through its brakes.
> So, yeah, lock-up can generate lots of heat from the brakes.

Enough to heat the drums, which are usually at least partway inside
the dish of the inner wheel, to a nice red glow.

> Those skid marks usually come from a lost supply line to the trailer
>air brakes, causing the trailing axles to "park." Most of the time that
>back axle will be lightly loaded compared to the axles under the front
>of the trailer.

Unless, as you noted, the truck is running with a full load, in which
case the rear axles may be loaded heavily unless the driver has
shifted the axles rearward, which he should have for non-city running.

> Drivers are supposed to balance the axles, but few do
>since it's a big pain in the ass.

Worse, with a partial load, it may not be possible to put any
significant weight to the rear. Load stops and straps or not, when
all you have is a handful of damned heavy pallets, they'll be up front
unless it's on a flatbed where there are a lot more tie-down options.

>Leaving you with one axle that's very
>likely to leave skid marks, and a bunch of axles that aren't. If you
>ever come to a site where a truck skidded to a stop on purpose by way of
>service brakes you'll notice a whole bunch of skid marks and it'll look
>like several trucks stopped in the same place. Most trucks have ABS now
>anyway, so those solid skid marks can only be generated by the failure
>mode and that's almost always from a lost trailer air line.

Bingo. It's a common enough failure that many drivers carry spares
for all three lines, and they're typically sold at most truck stops as
well.

>>Second, brake drums are substantially far away from rim beds, where
>>tire inflation air could be heated, to have any effect.

A brake drum at 900F which is in the vertical plane of the inner
wheel's frameward bead is quite capable of heating that tire to the
point where the surface begins to melt, which then drips onto the
brake drum and ignites.

>>Besides, what is "localized heat" from braking? The heat path from
>>brake drum to tire is via the rim dish that has a long\ thermal path to
>>pressurized air.
>
> I don't think that gap is substantial enough. I know it's a air gap
>and all, but that's a lot of heat being radiated. Truck tires do catch
>fire from excessively prolonged braking, so that heat must be getting
>across somehow. I figure it's through sheer brute force of enough heat
>to overcome any sort of inefficiency in transmission.

Yes. I regularly see the results of such fires in my travels. It
does, indeed, happen. The retired truck driver who lives across the
street has said on more than on occasion that a trailer brake overheat
may occur without the driver being aware of what's going on until it's
too late to do anything but stop, unhitch and hope. I've seen what
happens if the driver fails to unhitch a couple of times as well.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

[Werehatrack]

On Sat, 16 Oct 2004 05:51:15 GMT, "Leo Lichtman"
> wrote:

>
>"Werehatrack" wrote : "Yes," in response to Leo's question, "Are you sure
>about this?"
>^^^^^^^^^^^^^^^^^
>From what you have written, it is clear that you are knowlegeable on this
>topic--I believe you now. From the fact that you have seen a number of
>tires rupture in car fires, and the authority with which you speak on this
>subject, I assume that this is professional expertese. Are you a
>firefighter? Would you mind filling us in?

Not a firefighter, no, but I spent several years as a professional
mechanic, and I travel for sales events (and frequently talk to
professional drivers) quite a bit these days, so I see quite a few of
these failures and hear about more of them. I also used to share
space with an aviation engine overhaul shop many years ago, which is
where my familiarity with some aircraft issues comes from. And I read
a lot. Too much, in some cases.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

[Werehatrack]

On Sat, 16 Oct 2004 05:51:15 GMT, "Leo Lichtman"
> wrote:

>
>"Werehatrack" wrote : "Yes," in response to Leo's question, "Are you sure
>about this?"
>^^^^^^^^^^^^^^^^^
>From what you have written, it is clear that you are knowlegeable on this
>topic--I believe you now. From the fact that you have seen a number of
>tires rupture in car fires, and the authority with which you speak on this
>subject, I assume that this is professional expertese. Are you a
>firefighter? Would you mind filling us in?

Not a firefighter, no, but I spent several years as a professional
mechanic, and I travel for sales events (and frequently talk to
professional drivers) quite a bit these days, so I see quite a few of
these failures and hear about more of them. I also used to share
space with an aviation engine overhaul shop many years ago, which is
where my familiarity with some aircraft issues comes from. And I read
a lot. Too much, in some cases.
--
Typoes are a feature, not a bug.
Some gardening required to reply via email.
Words processed in a facility that contains nuts.

[Peter]

wrote:
> The problem with Nitrogen is that the molecules are very small.

No, N2 molecules are very similar in size to O2 molecules. These two
together constitute about 99% of dry air (78% nitrogen, 21% oxygen, 1%
argon and other gases).

> I've used both Nitrogen and Helium in my tires to race on the track because
> it is lighter than air.

Helium is lighter (4g/mole), but nitrogen (28 g/mole) is almost the same
weight as dry air (29 g/mole)[humid air is a bit lighter due to the
lighter (18 g/mole) water molecules].
>
> The lighter, smaller molecules in the Ni will more easily leak through the
> butyl or latex in your tubes and you will have to pump them up daily.

Nitrogen actually permeates through rubber slower than oxygen and would
therefore be marginally better in this regard than using air.
You may be thinking of carbon dioxide which does permeate rubber faster
than either nitrogen or oxygen and would require more frequent pumping.
It's also a heavier gas at about 40 g/mole.
>
> Jason
>
> "Erik Freitag" > wrote in message
> ...
>
>>My local Costco is advertising their use of nitrogen for automobile tire
>>inflation. They say nitrogen is a dry, inert gas used to inflate airplane
>>tires, off-road truck tires, military vehicle tires and race car tires for
>>improved performance.
>>
>>Apparently, the oxygen in compressed air is bad for tires, and I assume,
>>tubes.
>>
>>So, does topeak or zefal make a reasonably priced, frame-mounted nitrogen
>>generator?

[Peter]

wrote:
> The problem with Nitrogen is that the molecules are very small.

No, N2 molecules are very similar in size to O2 molecules. These two
together constitute about 99% of dry air (78% nitrogen, 21% oxygen, 1%
argon and other gases).

> I've used both Nitrogen and Helium in my tires to race on the track because
> it is lighter than air.

Helium is lighter (4g/mole), but nitrogen (28 g/mole) is almost the same
weight as dry air (29 g/mole)[humid air is a bit lighter due to the
lighter (18 g/mole) water molecules].
>
> The lighter, smaller molecules in the Ni will more easily leak through the
> butyl or latex in your tubes and you will have to pump them up daily.

Nitrogen actually permeates through rubber slower than oxygen and would
therefore be marginally better in this regard than using air.
You may be thinking of carbon dioxide which does permeate rubber faster
than either nitrogen or oxygen and would require more frequent pumping.
It's also a heavier gas at about 40 g/mole.
>
> Jason
>
> "Erik Freitag" > wrote in message
> ...
>
>>My local Costco is advertising their use of nitrogen for automobile tire
>>inflation. They say nitrogen is a dry, inert gas used to inflate airplane
>>tires, off-road truck tires, military vehicle tires and race car tires for
>>improved performance.
>>
>>Apparently, the oxygen in compressed air is bad for tires, and I assume,
>>tubes.
>>
>>So, does topeak or zefal make a reasonably priced, frame-mounted nitrogen
>>generator?

[Blair P. Houghton]

Leo Lichtman > wrote:
>I am convinced it is a gimmick. I picked up the brochure at the Costco tire
>shop, and studied it. The main "advantage" of nitrogen is that the molecule
>is slightly heavier than oxygen, so it seeps out of the tire more slowly.
>This, supposedly, results in less tendency toward underinflation. And, of

Fill tire to 110 psi with air.

It "seeps out" the 30% that isn't nitrogen.

Refill to 110 psi with air.

It "seeps out" the 9% that isn't nitrogen.

Refill to 110 psi with air.

It "seeps out" the 2.7% that isn't nitrogen.

and so on.

By the end of the month, you're riding on tires filled with
pure nitrogen (and bigger things) at 110 psi.

--Blair
"You need plutonium presta valve screws,
too. I just happen to be the sole U.S.
distributor for Three-Mile Island brand
plutonium presta valve screws..."

[Blair P. Houghton]

Leo Lichtman > wrote:
>I am convinced it is a gimmick. I picked up the brochure at the Costco tire
>shop, and studied it. The main "advantage" of nitrogen is that the molecule
>is slightly heavier than oxygen, so it seeps out of the tire more slowly.
>This, supposedly, results in less tendency toward underinflation. And, of

Fill tire to 110 psi with air.

It "seeps out" the 30% that isn't nitrogen.

Refill to 110 psi with air.

It "seeps out" the 9% that isn't nitrogen.

Refill to 110 psi with air.

It "seeps out" the 2.7% that isn't nitrogen.

and so on.

By the end of the month, you're riding on tires filled with
pure nitrogen (and bigger things) at 110 psi.

--Blair
"You need plutonium presta valve screws,
too. I just happen to be the sole U.S.
distributor for Three-Mile Island brand
plutonium presta valve screws..."

[Ken Pisichko]

This is just a Costco marketing strategy. The Costco "techies" could only
spout off what they were taught. They could give no chemistry background as to
why nitrogen was better, nor could they say what would happen if their pure
nitrogen filled tires were partially deflated due to the minus 40C temps this
coming winter and I'll have to pump up the tires at the local garage with
(GASP!!) ordinary compressed air.

In spite of what they use in dragsters and aircraft, for bicycles and land
vehicles going less than 100 mph, regular air even the polluted stuff) is
fine! I'll bet that Lance Armstrong was just using air during his last few
racing seasons ;-).

Leakage of air?? Well my 1972 Land Rover has been parked at leisure on my
brother's farm for about 14 or 15 years and the 20 year old tubes and tires
are still full of air - mind you they are not quite as "full" as they once
were. But they still do a fine job in 4WD in the muddy field when getting
cattle.

Remember that air is about 4/5 nitrogen....

Erik Freitag wrote:

> My local Costco is advertising their use of nitrogen for automobile tire
> inflation. They say nitrogen is a dry, inert gas used to inflate airplane
> tires, off-road truck tires, military vehicle tires and race car tires for
> improved performance.
>
> Apparently, the oxygen in compressed air is bad for tires, and I assume,
> tubes.

[Ken Pisichko]

This is just a Costco marketing strategy. The Costco "techies" could only
spout off what they were taught. They could give no chemistry background as to
why nitrogen was better, nor could they say what would happen if their pure
nitrogen filled tires were partially deflated due to the minus 40C temps this
coming winter and I'll have to pump up the tires at the local garage with
(GASP!!) ordinary compressed air.

In spite of what they use in dragsters and aircraft, for bicycles and land
vehicles going less than 100 mph, regular air even the polluted stuff) is
fine! I'll bet that Lance Armstrong was just using air during his last few
racing seasons ;-).

Leakage of air?? Well my 1972 Land Rover has been parked at leisure on my
brother's farm for about 14 or 15 years and the 20 year old tubes and tires
are still full of air - mind you they are not quite as "full" as they once
were. But they still do a fine job in 4WD in the muddy field when getting
cattle.

Remember that air is about 4/5 nitrogen....

Erik Freitag wrote:

> My local Costco is advertising their use of nitrogen for automobile tire
> inflation. They say nitrogen is a dry, inert gas used to inflate airplane
> tires, off-road truck tires, military vehicle tires and race car tires for
> improved performance.
>
> Apparently, the oxygen in compressed air is bad for tires, and I assume,
> tubes.

[VeloFlash]

> The problem with Nitrogen is that the molecules are very small.
> I've used both Nitrogen and Helium in my tires to race on the trac
> because
> it is lighter than air.
>
> The lighter, smaller molecules in the Ni will more easily leak throug
> the
> butyl or latex in your tubes and you will have to pump them up daily.
>
> Jason
>
> [/color]

My understanding was that nitrogen was used in tubular/single tire
with latex tubes as nitrogen escaped slower than "air".

Latex tubes at the end of a long day require pumping to rectif
pressure if using air

--
VeloFlash

[VeloFlash]

> The problem with Nitrogen is that the molecules are very small.
> I've used both Nitrogen and Helium in my tires to race on the trac
> because
> it is lighter than air.
>
> The lighter, smaller molecules in the Ni will more easily leak throug
> the
> butyl or latex in your tubes and you will have to pump them up daily.
>
> Jason
>
> [/color]

My understanding was that nitrogen was used in tubular/single tire
with latex tubes as nitrogen escaped slower than "air".

Latex tubes at the end of a long day require pumping to rectif
pressure if using air

--
VeloFlash

[Threeducks]

wrote:
> The problem with Nitrogen is that the molecules are very small.
> I've used both Nitrogen and Helium in my tires to race on the track because
> it is lighter than air.
>
> The lighter, smaller molecules in the Ni will more easily leak through the
> butyl or latex in your tubes and you will have to pump them up daily.
>

You're filling you tires with Ni? Nickel? How do you do that?

[Threeducks]

wrote:
> The problem with Nitrogen is that the molecules are very small.
> I've used both Nitrogen and Helium in my tires to race on the track because
> it is lighter than air.
>
> The lighter, smaller molecules in the Ni will more easily leak through the
> butyl or latex in your tubes and you will have to pump them up daily.
>

You're filling you tires with Ni? Nickel? How do you do that?

[George Herbert Walker]

wrote in message >...

> When does aluminum burn in air?

I take this to mean that aluminum will not burn in air in the
circumstances described, but that it may in other circumstances. If
so, here is a somewhat controversial example:

The Falklands War was the first, and perhaps last, proving ground for
the aluminum warship. Chemists and some others with a memory of the
periodic table, or with the knowledge that aluminum is a common
ingredient in rocket fuels and bombs, must have known what was coming,
although Margaret Thatcher, whose degree actually was in theoretical
chemistry, for some reason apparently did not. (Perhaps, some of us
fantasize, this was yet another reason why Oxford denied her an
honorary doctorate.) At least one of these floating absurdities, HMS
Sheffield, was hit with an Exocet missile, and naturally enough burned
with brutal intensity in fires that could not be extinguished or
controlled. These ships were total losses. Her Majesty's Royal Navy
also made the mistake of equipping the sailors with polypropylene long
underwear, and these two colossal errors of judgement were
contributors to the tragically high rate of severe and fatal burns the
British experienced during that war.

This account is controversial because some suggest: 1) It wasn't
aluminum, but aluminum-magnesium alloy; 2) The aluminum didn't burn,
but melted; and 3) the ships were mostly steel anyway. I tend to
disbelieve these rebuttals in part because I remember before the war
the descriptions of these ships as having substantial aluminum content
(and thinking oh-oh... as I did doubly when reading beforehand that
the sailors were using synthetic long underwear), and I remember how
fiercely they burned, unlike other ships that were not advertised as
being aluminum. Aluminum certainly burns quite easily in higher oxygen
content atmospheres. Aluminum armor also has a history in tanks etc,
and the majority negative assessment is also somewhat controversial-
perhaps Alcoa has Karl Rove working for it.

The stupidity of polypropylene underwear in such circumstances is not
controversial though.

[George Herbert Walker]

wrote in message >...

> When does aluminum burn in air?

I take this to mean that aluminum will not burn in air in the
circumstances described, but that it may in other circumstances. If
so, here is a somewhat controversial example:

The Falklands War was the first, and perhaps last, proving ground for
the aluminum warship. Chemists and some others with a memory of the
periodic table, or with the knowledge that aluminum is a common
ingredient in rocket fuels and bombs, must have known what was coming,
although Margaret Thatcher, whose degree actually was in theoretical
chemistry, for some reason apparently did not. (Perhaps, some of us
fantasize, this was yet another reason why Oxford denied her an
honorary doctorate.) At least one of these floating absurdities, HMS
Sheffield, was hit with an Exocet missile, and naturally enough burned
with brutal intensity in fires that could not be extinguished or
controlled. These ships were total losses. Her Majesty's Royal Navy
also made the mistake of equipping the sailors with polypropylene long
underwear, and these two colossal errors of judgement were
contributors to the tragically high rate of severe and fatal burns the
British experienced during that war.

This account is controversial because some suggest: 1) It wasn't
aluminum, but aluminum-magnesium alloy; 2) The aluminum didn't burn,
but melted; and 3) the ships were mostly steel anyway. I tend to
disbelieve these rebuttals in part because I remember before the war
the descriptions of these ships as having substantial aluminum content
(and thinking oh-oh... as I did doubly when reading beforehand that
the sailors were using synthetic long underwear), and I remember how
fiercely they burned, unlike other ships that were not advertised as
being aluminum. Aluminum certainly burns quite easily in higher oxygen
content atmospheres. Aluminum armor also has a history in tanks etc,
and the majority negative assessment is also somewhat controversial-
perhaps Alcoa has Karl Rove working for it.

The stupidity of polypropylene underwear in such circumstances is not
controversial though.

The problem with Nitrogen is that the molecules are very small.
I've used both Nitrogen and Helium in my tires to race on the track because
it is lighter than air.

The lighter, smaller molecules in the Ni will more easily leak through the
butyl or latex in your tubes and you will have to pump them up daily.

Jason

"Erik Freitag" > wrote in message
...
> My local Costco is advertising their use of nitrogen for automobile tire
> inflation. They say nitrogen is a dry, inert gas used to inflate airplane
> tires, off-road truck tires, military vehicle tires and race car tires for
> improved performance.
>
> Apparently, the oxygen in compressed air is bad for tires, and I assume,
> tubes.
>
> So, does topeak or zefal make a reasonably priced, frame-mounted nitrogen
> generator?

The problem with Nitrogen is that the molecules are very small.
I've used both Nitrogen and Helium in my tires to race on the track because
it is lighter than air.

The lighter, smaller molecules in the Ni will more easily leak through the
butyl or latex in your tubes and you will have to pump them up daily.

Jason

"Erik Freitag" > wrote in message
...
> My local Costco is advertising their use of nitrogen for automobile tire
> inflation. They say nitrogen is a dry, inert gas used to inflate airplane
> tires, off-road truck tires, military vehicle tires and race car tires for
> improved performance.
>
> Apparently, the oxygen in compressed air is bad for tires, and I assume,
> tubes.
>
> So, does topeak or zefal make a reasonably priced, frame-mounted nitrogen
> generator?

[Peter Cole]

"George Herbert Walker" > wrote in message
om...
> wrote in message
>...
>
> > When does aluminum burn in air?
>
> I take this to mean that aluminum will not burn in air in the
> circumstances described, but that it may in other circumstances. If
> so, here is a somewhat controversial example:
>
> The Falklands War was the first, and perhaps last, proving ground for
> the aluminum warship. Chemists and some others with a memory of the
> periodic table, or with the knowledge that aluminum is a common
> ingredient in rocket fuels and bombs, must have known what was coming,

>
> This account is controversial because some suggest: 1) It wasn't
> aluminum, but aluminum-magnesium alloy; 2) The aluminum didn't burn,
> but melted; and 3) the ships were mostly steel anyway. I tend to
> disbelieve these rebuttals in part because I remember before the war
> the descriptions of these ships as having substantial aluminum content
> (and thinking oh-oh...

Both sides of the argument: http://www.g2mil.com/aluminum.htm

It sounds to me that the aluminum didn't burn.

[Peter Cole]

"George Herbert Walker" > wrote in message
om...
> wrote in message
>...
>
> > When does aluminum burn in air?
>
> I take this to mean that aluminum will not burn in air in the
> circumstances described, but that it may in other circumstances. If
> so, here is a somewhat controversial example:
>
> The Falklands War was the first, and perhaps last, proving ground for
> the aluminum warship. Chemists and some others with a memory of the
> periodic table, or with the knowledge that aluminum is a common
> ingredient in rocket fuels and bombs, must have known what was coming,

>
> This account is controversial because some suggest: 1) It wasn't
> aluminum, but aluminum-magnesium alloy; 2) The aluminum didn't burn,
> but melted; and 3) the ships were mostly steel anyway. I tend to
> disbelieve these rebuttals in part because I remember before the war
> the descriptions of these ships as having substantial aluminum content
> (and thinking oh-oh...

Both sides of the argument: http://www.g2mil.com/aluminum.htm

It sounds to me that the aluminum didn't burn.