I'm still trying to figure out how pista tire pump heads work. My pump has a dual schrader / pista head. I figured out how to use it in both modes. I just don't understand how it works in Pista mode. I'm guessing it just clamps on tight around the pista shaft. Once you get the pump internal pressure over the tube internal pressure, the pista valve opens?

Note: previously, I used one of those pista to schrader converters and my shop air compressor to pump up the tires of my bike with pista tubes.