Don't know if this has been discussed before, but leave it to me to be redundant if it has. Anyway, as we are preparing for our first outing to escape the snow, I dutifully began checking the tire pressures only to have one valve decide to let more air out than I could put in. I quickly put the cap back on and ran to an auto parts store and bought a tire valve extraction tool. A couple of turns with it and all was well. Something to be aware of, I guess. The little valve in the stem had worked itself loose is all. I now have a new tool to take with us. Only cost $5.00 and saved a lot of potential grief!