"Quiver" is a silly name for the group of bikes one owns and rides. If you've shot bow'n'arras much, you know that the vast majority of archers want every arrow in their quiver to be as much like all the others as possible, because consistency is the basis of accuracy. With bikes, if you own a number of bikes, usually no two are alike. You bought each one for its own unique properties that set it apart from the others. "Stable" conveys that idea - horses are individuals, so it's not a bunch of identical things, so "stable" is okay by me. I've used it occasionally. But "steed"? That's a bit pretentious, somehow, IMO.

WRT tires, I agree that "tubs" is not, at least in speech, an abbreviation of "tubulars", and "sew-ups" is far more specifically descriptive. Up till tubeless was invented, all tires had tubes, so "tubular" could describe all of them, but "sew-up" clearly distinguishes one type. I suppose you could also call them "stick-ons", but that doesn't sound as good as "sew-up".