If i were you i'd deflate them, tyre soap the beads (no need to break the bead) then re-inflate to 60psi-ish then back to standard. If there is a slight seating problem this should cure it. Also buy a couple of quality valve-caps, the type with O-ring seals.I'm extremely surprised I didnt have more problems. Hopefully, this just happened over the winter. I will check regularly now.