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Speaker 1: Welcome to Brainstuff from house stuffworks dot com where smart happens. Hi.

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Speaker 1: I'm Marshall Brain with today's question, why don't they use

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Speaker 1: normal air when they pump up race car tires? Many

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Speaker 1: race car teams use nitrogen instead of air in their

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Speaker 1: tires because nitrogen has a much more consistent rate of

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Speaker 1: expansion and contraction compared to the normal air that we breathe. Often,

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Speaker 1: a half pound of pressure will radically affect the traction

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Speaker 1: and handling of a tire. With track entire temperatures varying

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Speaker 1: over the duration of a race, the consistency of nitrogen

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Speaker 1: is needed so that the team and the driver can

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Speaker 1: maintain their sanity. Nitrogen pressure is more consistent than normal

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Speaker 1: air pressure because air typically contains varying amounts of moisture

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Speaker 1: due to changes in the relative humidity on race day.

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Speaker 1: Water in the air causes that air to be inconsistent

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Speaker 1: in its rate of expansion and contraction. So a humid

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Speaker 1: race in the southeast United States or a dry race

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Speaker 1: in the desert western United States could make for unpredictable

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Speaker 1: tire pressures as the tires heat up and cool down

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Speaker 1: during the race. If you use dry nitrogen, which contains

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Speaker 1: no humidity. You don't have to worry about these inconsistencies.

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Speaker 1: Nitrogen is also used in the high pressure tires of

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Speaker 1: large and small aircraft. It turns out that many tire

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Speaker 1: shops will now sell you nitrogen filling for your tires

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Speaker 1: if you're willing to pay extra for it. Is this

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Speaker 1: a good idea? Chances are, in your normal day to

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Speaker 1: day driving, a little bit of tire pressure change isn't

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Speaker 1: going to make that much difference to you, if any

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Speaker 1: at all. And the other ideas that a tire shop

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Speaker 1: will use to try to sell you the nitrogen usually

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Speaker 1: are red herrings. They'll talk about things like rust your

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Speaker 1: inner rims, or attacks by oxygen atoms on the inner

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Speaker 1: part of the rubber of the tire, all kinds of stuff.

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Speaker 1: Almost all of this falls into the category of urban legend.

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Speaker 1: But if you want to pay extra for dry night

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Speaker 1: virgenior tires, it certainly isn't gonna hurt anything. For more

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Speaker 1: on this and thousands of other topics, doesn't how stuff

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Speaker 1: works dot Com, and don't forget to check out the

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Speaker 1: brain stuff blog on the how stuff works dot Com

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