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0 pointstmh88j3y ago0 comments

>That's what they told me at the dealership too. I asked "larger than what? Air is a mixture that's already 78% nitrogen." Didn't get an answer.

No idea about molecule size, but the reason for nitrogen is that it expands less than air when heated, so tire pressure doesn't change as much when driving hard on a track.

> As far as the lower moisture content, couldn't they pass the air through an air dryer before filling the tire if it was that much of an issue?

Yes, this point is some dealership BS. Pretty much every auto shop will have a dedicated air line for filling tires, if not the whole system with an air dryer.

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2 comments · 2 top-level

mikestew3y ago

When I was a pro mechanic, the whole compressed air system had moisture removal, because I don't want that shit in my air tools, either. I don't know about Costco, but of the shops I know of, it's one big compressor for tools, tires, etc.

growse3y ago

> >That's what they told me at the dealership too. I asked "larger than what? Air is a mixture that's already 78% nitrogen." Didn't get an answer.

> No idea about molecule size, but the reason for nitrogen is that it expands less than air when heated, so tire pressure doesn't change as much when driving hard on a track.

Pressure/temperature/volume for any gas are governed by the ideal gas law, which doesn't care what your molecules are.

(Sure, it's an approximation, but certainly one that's imperceptibly reliable enough for car tyres).

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