Well, I wrassled with the hissing snake again tonight. I confidently tapped to break the seal (only worked on the rear tire, alas) and even more confidently pressed the pump head on... since now I know the difference between locked and unlocked.

Still: some hissing whenever I'm not pumping. Though I was slightly more successful than last time... the tire didn't get completely flat.

Is there supposed to be complete silence when you're not pumping, or is some hissing to be expected?

Hisssssssssssssss....