Cold weather takes air out of your tires

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OK, I never believe all the BS on tv, but they just had a thing on tv, The Early Show) about winter driving. Most of what they said was right, but they said that cold weather takes air out of your tires...
Ummmm, I dont buy that..... Yes, cold makes metal shrin, in fact I recall many years ago there was a long railroad bridge that shrunk so much in the cold that they had to shut it down and put supports under the ends because the ends were coming off the supports. and I have also seen the opposite in the summer when it gets real hot, long stretches of freeways will actually buckle because the concrete expands and has no where to go.
With that in mind, I would assume the air volume in tires might also shrink, and the metal rim may shrink in a very small amount, but I dont see how it could "take air out of the tires". At the same time, does air shrink in the cold? I really dont know. I just know that metals and concrete does. Unless someone knows something different, I think this thing about tires losing air is false information. What do you think, or know about this? I'm curious now.
LM
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On Jan 31, 8:05 am, snipped-for-privacy@invalid.com wrote:

I'd say it's a sad reflection on the current state of education in the USA. The effect is described in Charles Law, which goes back several centuries. And the law is about gases and temp, not tires.
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Yes, it does shrink and pressure is reduced. The "lets air out" is just some idiot that either never had a physics class or does not know how to describe what happens. The only thing even more sad, is people believe him and never question "why?" You may not have know the exact answer, but you were smart enough to know it did not seem right and then sought more information. That is how we learn
When tires heat up, the pressure increases. While they may have minor seasonal changes, don't add extra because they do get back up to normal after some driving. Tire flex generates heat.
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Often I find that the idiot that said "lets air out" knows what he is talking about but knows explaining Charles Law to people during a TV ad is a lost cause.
Jimmie
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on 1/31/09 7:25 AM Ed Pawlowski said the following:

try to check tire pressure at room temperature. if you check at 0 F and fill to pressure on the label by door frame, the air will be more dense and then when the tires heat up from driving the tires may be "over-inflated". But make sure to use the label on the door frame (not the label on the tire).
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On Sat, 31 Jan 2009 07:05:08 -0600, letterman wrote:

Which raises the question in my mind....
Which TV news source is the most inaccurate when it comes to science and technology: CBS or CNN?
(CNN is noted for hyping electric cars which "don't cause pollution of any kind" and also don't question where the electricity out of the wall socket comes from.)
Phil
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On Sat, 31 Jan 2009 09:11:45 -0600, Phil Again wrote:

Noted by who? Do you have a cite for them making that claim? Of course what might have actually been said was that electric cars "emit" no pollution which is completely different than saying that they don't "cause" any.
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On Sat, 31 Jan 2009 08:01:12 -0800, trader4 wrote:

It is true that they "emit" zero pollution (or very close to zero) so I see no lies or irresponsibility in that statement.
While the plant producing the electricity does produce pollution (something everyone is aware of without being told), the amount of pollution needed for the electricity to move an electric car 100 miles is a lot less then the pollution created to do the same with in internal combustion engine.
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yes,but they do need to remind the public about the electric source pollution.

Not nuclear plants. IIRC,20% of US power generation. (Needs to be 70% or more.)

HMM,how much mercury do coal-fired plants emit,or their contribution to acid rain? oil/nat.gas isn't used extensively for electric power generation.
--
Jim Yanik
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Jim Yanik wrote: ...

Au contraire...particularly gas generation is moderately sizable. It is region-dependent on just how much, of course.
Let's see, I've been doing some work on trying to put some understanding and context on a statement our esteemed gun'nor made in her "State of State" address and so happen to have a bunch of the EIA data handy...
http://www.eia.doe.gov/cneaf/electricity/epm/table1_2.html
Annually on a US-basis, it runs about half nuclear. Not huge, but not insignificant.
And, unfortunately, while it does have the advantage of being lower in CO2/MWe than coal, imo it's a terrible waste of the resource which is far more valuable as feedstock and for heating, etc., and it's a shame we're using it as we are. A lot of this is the result of the former emphasis away from coal that caused a big shift in the gas turbines as utilities could manage to build "peaking" units where they couldn't get permitting for baseload. In some areas these eventually became nearly baseload as demand continued and still were unable (or unwilling in regulatory climate) to build other baseload units.
It's in that regard (siting of a proposed new facility here) that I've been looking into our Governor's lament (which appears so far to be as I thought when I heard it--a well-chosen, manufactured statistic that sounds bad for political effect).
--
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Jim Yanik wrote:

Or hydroelectric. Or wind. Or geothermal. Or chemical (i.e., batteries). Or electric eels. Or cat fur on a dry day.
And before anyone says a cat can't move a car, the cat can if you whip it.
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Of course it's irresponsible. It's like spewing about the health benefits of something like taking an aspirin a day to help reduce risk of heart attack without mentioning that there are potentially side effects and it isn't recommended for everyone.
In this case, the media is so in love with the notion of electric cars, that they don't want to say anything that might diminish their miracle like status. And in this case, it's that the electricity still has to come from somewhere. All your doing is transfering the energy generation and the problems that come with it, to someplace else. Actually, you're doing more than that. You're also introducing a distribution system, with significant losses into the equation. And yet, for some curious reason, you almost never hear this mentioned or discussed in the mainstream media.
This is a very real issue and if electric cars are going to play a signficant role in the future, than where the electricity is going to come from needs to be adressed.

You sure about that? Especially since we get most of our electric power from coal? And does it include the old coal plants in OH, that are spewing acid rain and CO2 into the atmosphere? I'd especially like to see any data on CO2 emissions, because I'd be willing to bet that by the time you mine coal, transport it, burn it to make electricity, then send it 500 miles to where it's used, then convert it to DC, store it into a battery, etc, it generates more CO2 than using gasoline in a smilar power engine/car.
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I've heard that the chemicals needed for making electric car batteries are worse than what's used for a normal car. The expen$e and chemicals used for electric cars are far worse than the usual cars. No, I don't remember where I heard this.
--
Christopher A. Young
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Dude!!!!
Where have you been???
Just last fall when the Auto Industry was looking for US Gov't loans to bridge until credit / banking problems clear up, CNN ran stock footage of electric cars and (reading the script) did not use the word "emit."
Next time Auto Industry is in the news again, or electric cars, just tune into CNN Headlines News anytime between 9:00am to 3:00pm weekdays and you will hear it being repeated every 1/2 hour or so. The Words "emit" are never said. Electric cars, per Headline News, are non-polluting.
Seriously, dude, those CNN Headline bubble-headed news-readers really do call electric cars "non-polluting" and they do state "don't cause air pollution."
Better yet, wait for Hydrogen fuel cars to come back into the news and listen for CNN's take on those non-fossil fuel dependent cars. (But where do the hydrogen come from? Hydrocarbon oil maybe??)
Trust me, the CNN newsreaders get science wrong between 9:00am and 3:00pm every weekday. Aside: not claiming they are 100% correct on other subjects, however they come close on fashion and Hollywood news though.
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snipped-for-privacy@optonline.net wrote:

I agree but suspect a troll as his language command is adequate for maybe a high school graduate.
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The law in question here is called Boyles Gas Law. It states that:
PV=nRT
where: P = pressure of the gas V = Volume of the container n = number of molecules of the gas R = the universal gas constant T = temperature
So, if temperature decreases, and all else stays the same, pressure goes down proportionally.
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Andrew wrote:

I always get Boyles and Charles mixed up but what you state is the ideal gas law which is easier to remember:
http://en.wikipedia.org/wiki/Gas_laws
Any high school graduate should a rough idea of temperature/volume/pressure relationship of gasses. It is also good to know that temperature is in degrees Kelvin and difference between pressure in a hot and cold tire is only a few pounds.
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On Jan 31, 8:05�am, snipped-for-privacy@invalid.com wrote:

HEADS UP IF YOU HAVE ALUNIMUM WHEELS:(
They corrode slowly at the bead, when it gets cold you may get a flat.
found this out on my wifes old car, constant yearly flats.
she drove on and ruined one wheel, which unable to get a matching one got a steel one from a auto junkyard. in the next 2 years all remaining tires went flat except the one on the steel wheel.
asked tire store who showed me corrode wheel.
Replaced all wheels with steel ones last flat that car ever had:)
Pressure does drop with cold but add a alunimum wheel and flat is result:(
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On Sat, 31 Jan 2009 07:05:08 -0600, snipped-for-privacy@invalid.com wrote:

Provided there are no leaks in the tire, the same number of molecules of air remain the same. A general understanding of gas laws (high school chemistry) makes sense of it. The long and skinny of all of this is check your tire pressure at least monthly--a digital pressure gauge makes it fast and easy.
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On Sat, 31 Jan 2009 07:05:08 -0600, against all advice, something compelled snipped-for-privacy@invalid.com, to say:

It doesn't. But as air gets colder, it gets more dense.
You can see it in action. Take an empty two liter soda bottle, and place it somewhere warm with the cap off. Over the heat register will do.
When you are sure it's up to room temperature (about an hour, I'd guess), put the cap on tightly, and place the bottle into your freezer. Leave it there for a day, and then take a look at it.
The air that was in it didn't go away, it just took up less space because it is now more dense. That's why the bottle is all smushed up looking. The same thing happens with tires.
I never noticed it to be a problem, though.
--

Real men don\'t text.

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