Honda Fit Tires..

Looking at a 2010 Honda Fit and the dealer says the tires are filled
with nitrogen. Can I continue to add air or do I have to use nitrogen?

It also comes with a tire pressure monitoring system. Is there anyway to
turn that off? I check my tires once a month.

I guess my real questions here are is it necessary to fill tires with
nitrogen and is it necessary to constantly monitor my tire pressure?

 

Please, do us all a favor and go enroll in community college and take a
physics class, and ask the professor what is the makeup of the
atmosphere we breathe....

.....and then come back and tell us your decision on this pressing issue.

Why do you want to turn that off? It sure sounds like you don't know
what it does.

 

Aren't you the helpful one? Lets see, is it: 78 percent nitrogen, 21
percent oxygen, and 1 percent other gases by volume?

This is the first time I've heard of nitrogen in tires. Seems like a
more of a marketing tool than a necessity on a Honda Fit.

Two for two on helpful! I guess it, duh, monitors the tire pressure? If
you don't know the answer, why reply? Please do us all a favor and stop
replying when you don't know the answer.

Or do you know if it can be turned off? Probably not.

 

The tire pressure monitoring system is federally mandated...and no,
you can't turn it off.

 

Guess I missed that.

http://www.nhtsa.gov/cars/rules/rulings/tirepresfinal/index.html

Sure enough. Does the TPMS have a dedicated fuse?

Do you have a car with this on it? If a person isn't going to check
their tires every so often, is some kind of federally mandated
monitoring system going to change that behavior? Can't one just
disregard the warning?

Please be patient with me, the last time I bought a car was 1993. I'm
not kidding. My 1993 Pathfinder came with air in the tires that I monitor.

 

There are those that claim it is an advantage.....but it would be so
minor, it's not worth the hassle. Most anyone can have a home air
compressor, not many have bottled nitrogen (I have it at work where
there are advantages to using it in process and storage, but my car
tires, not!).

 

Guess I missed that.

http://www.nhtsa.gov/cars/rules/rulings/tirepresfinal/index.html

Sure enough. Does the TPMS have a dedicated fuse?[/QUOTE]

tell us all why you DON'T want a light to come on when a tire has gone
significantly below the level of the other tires.

 

Aren't you the helpful one? Lets see, is it: 78 percent nitrogen, 21
percent oxygen, and 1 percent other gases by volume?[/QUOTE]

So you know your tires are getting filled with mostly nitrogen already.

And you think getting rid of the oxygen does...what?

 

Two for two on helpful! I guess it, duh, monitors the tire pressure? If
you don't know the answer, why reply? Please do us all a favor and stop
replying when you don't know the answer.

Or do you know if it can be turned off? Probably not.[/QUOTE]

As you know by now, it is mandated by federal law.

It monitors the tire pressure. You have yet to tell us why you want to
pull the fuse and turn it off.

You have yet to tell us how that system interferes with your life.

 

"the dealer says". that should have been a clue right at the start -
dealers say lots of things which aren't true. in this case, it's called
"keep the customer coming back".

air works fine.

you don't want to turn it off - if you get a nail in your tire, it might
not flat immediately, but leak faster than your once-a-month schedule
and therefore be dangerous, both to you and other road users.

no and yes. tpms has a limit below which it triggers the alarm - it's
not an active gauge. you should continue to monitor actual tire
pressure in the normal way

 

It appears to be the latest thing. I looked at a Venza and it's tires
were filled with nitrogen. My car buddy says it's a load of hooey since
air is mostly nitrogen anyway. Using canned nitrogen instead of the gas
station air will keep moisture out of the tires. But I have a little
tire compressor that doesn't produce moisture.

OK, I hadn't talked to my car buddy before I posted my questions. He was
out of town. Air it is!

Good point. I just thought it was another un-necessary warning light but
I see what you're saying. I've read in some other forums that the
sensors can be pretty sensitive to minor pressure changes but it's just
another light and better safe than sorry.

Thanks for your very helpful reply.

 

xample.com:

So you know your tires are getting filled with mostly nitrogen
already.

And you think getting rid of the oxygen does...what?
[/QUOTE]

eliminates corrosion and oxidation inside the wheel.

--
Jim Yanik
jyanik
at
localnet
dot com

 

Do you think corrosion inside the wheel is a significant problem? I
certainly don't.

Most of the places filling tires with "Nitrogen" are using at best 95%
nitrogen, not "pure" nitrogen. The main advantage (assuming there is one) is
the lack of moisture in the air. However, tires are porus, and I suspect
that even if you start out with 95% nitrogen in a few months you'll find
that you are closer to atmospheric percentages.

Ed

 

that's really not an issue.

there are two "advantages" to nitrogen, both of which are highly
marginal for normal road cars.

1. better thermal pressure stability. that's why you'll find some
racers use it so pressures don't change as much when the rubber's
burning, but road cars don't get their rubber anywhere near that hot.

2. tires take longer to lose pressure. air diffuses through rubber,
both inwards and outwards. if you fill a tire with 95% nitrogen, at the
same time as some nitrogen is diffusing out, oxygen will diffuse back in
[look up "partial pressures" on google if you want a detailed
explanation] and thus make it seem that the pressure is being maintained
slightly better.

but these two are completely irrelevant for normal driving and if the
tires are checked regularly.

 

HOW is oxygen going to "diffuse back in" to a PRESSURIZED tire,from
atmospheric pressure? It will NOT.

and Oxygen DOES react with the carbon in tires,and not in any good way.

--
Jim Yanik
jyanik
at
localnet
dot com

 

ok, i acknowledge that this may sound counter-intuitive, but if you know
the science, you will understand. that's why i said to look up partial
pressures. essentially, just like a high concentration of nitrogen in a
tire is seeking to dilute the outside air, the relatively high
concentration of oxygen outside the tire is seeking to dilute the
nitrogen inside - because the tire is a [slowly] permeable membrane.

not quickly enough to make any practical difference to an ordinary user
driving ordinary mileage.





further reading:
<http://en.wikipedia.org/wiki/Molecular_diffusion>

 

jim beam wrote:

Don't you mean "counterdiffusion" rather than "partial pressures"?

<snip>

 

Jim Yanik wrote:

<snip>

Actually, given that a tire is permeable to O2, I believe it will if the
partial pressure of O2 inside the tire is less than the partial pressure
of O2 outside the tire.

Let's say the tire is inflated with 95% N2 and 5% O2 to 29.4 PSIG (which
is 3 atmospheres absolute pressure). The partial pressure of O2 is 3 *
..05 * 14.7 = 2.2 PSI. The partial pressure of O2 outside the tire is
..21 * 14.7 = 3.1 PSI. Holding all else constant, O2 would diffuse into
the tire until the partial pressure of O2 in the tire reaches 3.1 PSI.

 

the partial pressures provide the diffusion gradients...

 

Also, I just did a Google search and it seems that tires are much more
permeable to O2 than to N2--nearly 4x. Even Consumer Reports found a
difference in actual testing. Check out, for example:

http://home.comcast.net/~prestondrake/N2_FAQ_Q04.htm
http://www.getnitrogen.org/pdf/graham.pdf
http://blogs.consumerreports.org/cars/2007/10/tires-nitrogen-.html
http://blogs.consumerreports.org/cars/2007/10/nitrogen-tires-.html

However, perhaps unsurprisingly, I see nobody talking about
counterdiffusion (N2 diffusing out as O2 diffuses in). This is probably
because the gain in O2 pressure is more than offset by the loss in N2
pressure. (The tires are less permeable to N2 but there's a lot more of
it and the partial pressure differential is much higher. Still using
my example above, the partial pressure of N2 is 3 * .78 * 14.7 = 34.4
PSI. The partial pressure of N2 outside the tire is .78 * 14.7 = 11.5
PSI. This 22.9 PSI differential is about 25 times as large as that for
the PPO2s, so even at 1/4 the permeability the N2 pressure loss is about
6 times faster than the O2 gain if I've done all the math right.)

Me? I just use very dry air (scuba breathing air) for tire inflation
and check the pressure once in a while. Life is complicated enough
without looking for N2 tire fills, and the temperature variations in the
Northeast cause greater seasonal pressure differences than an N2 fill
would avoid anyway.