Schrader Valve Factoids

At this point, I rarely touch a Schrader valve for anything, let alone bicycle tubes. All the Feckless tubes are Presta, although our CO2 inflator works for both Presta and Schrader. In response to a customer question, I ended up learning some interesting things about Schrader valves.

Presta Valves

CO2 Cartridge Pressure

At room temperature, a CO2 cartridge is pressurized at around 850 PSI. That’s a lot of pressure!

Valve Core Schematic

Opening Pressure

Schrader International defines Opening Pressure as “This is the typical air pressure necessary to overcome the resistance of the spring that keeps the valve closed, allowing air to pass through.” This depends on the spring used in the valve core, and is typically around 40-60 PSIG, although it can go as low as 0.2 PSIG or as high as 90+ PSIG. The PSIG unit is used to refer to a delta in pressure, not absolute.

Important if you were, say, riding your bike in the vacuum of space or a hyperbaric chamber.

Also means that you don’t actually have to depress the valve pin, as long as you have sufficient external pressure, like a high-pressure bike pump or CO2 inflator. Low-pressure pumps (car pump?) would still need to depress the pin.

Early Advertising

This Schrader advertisement from 1921 is referenced by Wikipedia as en early example of sex in advertising. Nothing says sexy like Schrader valves!

1921 Schrader Valve Ad

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