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I think everyone has...try a search on Helium.
 

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squish is good
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I know some car racing teams use Nitrogen because its inert, and isn't supposed to change too much under pressure. I have no idea of the chemistry behind it, and I believe the performance gains are minimal when talking normal use. If anything its limited to super high performance stuff that has to do with rotational mass at speeds of 180mph+. I can't imagine it making a big difference on a bicycle of any sort. So the short answer is, air should be as good as anything at the speeds we normally experience.
 

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dennis rides Scott said:
It will not work. The tyres will loose pressure before you have used the bike. No tyre is airtight enough to hold helium.
Something like that. I'm pretty sure that the microscopic pores in the tube are bigger than a Helium atom, so it will seep out much quicker than regular old air.
 

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Doesntplaywellwithmorons!
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Nitrogen doesn't expand at all under temperature. Its used instead of normal air because there's no humidity/moisture factor to deal with, which is where the expansion and condensation with temperature changes come into play. Its these changes that annoy auto racers because it can alter how the tire behaves on the track over the course of just a few laps. Bad enough they have to deal with how the rubber tread behaves at different temperatures. They don't wanna have to deal with their tire pressure changing 10% as well. As to helium, its problem is the size of the molecules vs the porousity of the butyl/rubber tubes. Its only of a practical application on track bikes at the Pro/Olympic level... bikes which only have to be used for a few laps at a time, and can immediately be inspected/serviced by a mechanic after each race. You might try it as a pro DH-racer, because your race is over in 6 mins anyways, but its all the waiting around before each time down the mountain where you'd have the issues.

Anyways, this is a REALLY old subject on mtbr, its come up at least once every six months for the past 9 years.
 

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A tire internal volume is about 0.14 ft3.

Air at 60 psi and 60 f weighs 0.38 lbs/ft3.

Air in a tire weighs 0.0532 lbs or 24 grams.

He would weigh 2/28.9*24 or 1.7 grams

The wieght savings is about 22 grams per tire.

Yes it would leak out faster but He balloons last at least several days.

And Dee eight N2 versus air (air is 71% n2) have almost exactly the same pressure/temp relationship so the diffenernce is in the humidity.
 

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Discussion Starter · #20 ·
Can you run by me how you got the internal volume of a tire? When I do a brief ballpark figure calculation it seems like it should be higher.
 
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