Both Joe and Jess are right about carrying extra stems and the tool .3 weeks ago, I had to take some extra air out while on Brigantines beach. While airing back up, I heard the dreaded hissing noise coming from the valve
. Late Sun evening, no place open, with the camper on, so changing the tire would have been a PIA. Cranked the cap down as hard as I could and hoped to make it home. Paid $1.98 for the valve tool and fixed the leak in 10 seconds.
Good Luck, Joe.