Why don't they use normal air in race car tires?

Race car tires are often filled with nitrogen because nitrogen pressure is more consistent than air pressure. In this episode, Marshall explains why nitrogen is better for race cars -- but not for regular vehicles.

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Episode Transcript

Speaker 1 (00:00):
Welcome to Brainstuff from house stuffworks dot com where smart happens. Hi.
I'm Marshall Brain with today's question, why don't they use
normal air when they pump up race car tires? Many
race car teams use nitrogen instead of air in their

(00:23):
tires because nitrogen has a much more consistent rate of
expansion and contraction compared to the normal air that we breathe. Often,
a half pound of pressure will radically affect the traction
and handling of a tire. With track entire temperatures varying
over the duration of a race, the consistency of nitrogen

(00:43):
is needed so that the team and the driver can
maintain their sanity. Nitrogen pressure is more consistent than normal
air pressure because air typically contains varying amounts of moisture
due to changes in the relative humidity on race day.
Water in the air causes that air to be inconsistent
in its rate of expansion and contraction. So a humid

(01:05):
race in the southeast United States or a dry race
in the desert western United States could make for unpredictable
tire pressures as the tires heat up and cool down
during the race. If you use dry nitrogen, which contains
no humidity. You don't have to worry about these inconsistencies.

(01:26):
Nitrogen is also used in the high pressure tires of
large and small aircraft. It turns out that many tire
shops will now sell you nitrogen filling for your tires
if you're willing to pay extra for it. Is this
a good idea? Chances are, in your normal day to
day driving, a little bit of tire pressure change isn't

(01:47):
going to make that much difference to you, if any
at all. And the other ideas that a tire shop
will use to try to sell you the nitrogen usually
are red herrings. They'll talk about things like rust your
inner rims, or attacks by oxygen atoms on the inner
part of the rubber of the tire, all kinds of stuff.

(02:08):
Almost all of this falls into the category of urban legend.
But if you want to pay extra for dry night
virgenior tires, it certainly isn't gonna hurt anything. For more
on this and thousands of other topics, doesn't how stuff
works dot Com, and don't forget to check out the
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