My initial feeling is that they would be overkill. Too much weight for the air capacity they hold. I'm basing this on my experience with scuba cylinders which hold 2400-3500 psi depending on the model. Divers often use an air chuck and their regulators to fill tires. A filled scuba tank holds 80cuft generally. Fire extinguishers make a better option. See Roger Brown's site. They are light and hold about 200psi. At 100 psi you've only got a couple of cuft of 1atm air.

Good thinking though. It's nice to adapt "waste" to another use.

Lars,
Gold Coast Cruisers |My 4Runner