Stealing air from cars.

http://lifehacker.com/5669493/make-an-automatic-bicycle-pump-to-steal-air-from-cars

Check this out, I carry C02 with me in case my pump breaks, but if I had one of these I would be set.

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Right

The psi pushing out has to be higher than the psi going in and most if not all car tires are at about 40 I think. Neat idea but sure wouldnt help with my 90+psi tires.